Exploring The Advantages And Disadvantages Of Using Biodiesel Engineering Essay

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The diesel engine is an internal combustion engine in which the high pressure and temperature conditions associated with the compression stroke are utilized to ignite and burn the diesel-fuel mixture within the combustion chamber. The energy released from this process is harnessed and is called the power stroke of the engine. The diesel engine differs from the gasoline engine in the fact that there is no spark plug used and instead the compression heat ignites the diesel-fuel mixture and this is referred to as compression ignition. Another difference between the gasoline engine and the diesel engine is that, the compression ratios employed in spark ignition engines vary from 5-10 whereas compression ratios employed in diesel engines vary from 11-15. Thus, the actual thermal efficiency of the diesel engine is far more than that of other external and internal combustion engines.The diesel engine works on the Diesel cycle(heat addition at constant pressure) and was invented by Rudolf Diesel in 1897.

The diesel fuel on compression catches fire and combusts releasing the energy to run the engine. There are a number of fuel characteristics associated with this like cetane number, viscosity, etc.

Cetane number of a fuel is the percentage of cetane present in a cetane-methyl naphthalene mixture. It is a measure of how quickly the diesel fuel combusts or catches fire. It is particularly of interest in cold starting of engines, where a fuel with higher cetane number will start the engine without much trouble and less delay. In short, a fuel with higher cetane number will ignite faster under compression and burn completely giving maximum brake power output.

Viscosity is nothing but the resistance that a fluid offers to flow. This factor interferes with the fuel injection process.

With rising crude prices, there has been a lot of research into finding alternative fuels and a few examples are mentioned below.

Dimethyl ether is one among these alternatives owing to a very good cetane number of 55 with the plus side that it can be produced as biofuel.

Other additives such as Alkyl nitrates eg. 2-ethyl hexyl nitrate [1]) and di-tert-butyl peroxide also improve the cetane number.

Generally, when biodiesel is prepared from plant or vegetable oils, the cetane number we get ranges from 46 to about 52.

With depleting reserves of petroleum and environmental concerns, there is a gradual shift towards greener biodiesel. Biodiesel is manufactured from vegetable oils or animal fats and is biodegradable and owing to their almost zero sulfur content generates far lesser SOx emissions than petro diesel.

1.2 A BRIEF INTRODUCTION ON BIODIESEL

Biodiesel is an alternative fuel which is clean and contains no petroleum. It is fuel made from renewable sources and can be used in compression ignition engines with slight or even no modifications. It is biodegradable and emission levels are far less than those produced when running on conventional diesel. It can be made from vegetable oil, animal fat or even waste cooking oil.

1.2.1 HISTORY AND BACKGROUND

The transesterification of vegetable oil involved in making biodiesel was performed in 1853 itself by J. Patrick and E. Duffy. The first diesel engine by Rudolf Diesel was even run on peanut oil and its working was perfect. With depleting reserves of petroleum, environmental disasters involved with oil spills and the shift in thinking towards green practices, such renewable fuels are the answer to a better future. Biodiesel is available in fuel stations across Europe and is steadily coming into everyday use. Emission levels have again been a cause for concern and biodiesel has much lower sulphur content than conventional diesel. Biokerosene is another product both produced and patented by the Brazilian scientist, Expedito Parente which is awaiting certification from Boeing and NASA for use.

1.2.2 RELEVANCE OF BIODIESEL

1.2.2.1 Advantages

Biodiesel has many advantages over conventional diesel or petro diesel. Firstly, biodiesel has a much higher cetane number and offers better lubrication. It reduces wear in the fuel systems and improves life of the fuel injection system when used as low blends in high pressure systems. The energy density of biodiesel is comparatively lesser than that of petro diesel, about 37.27 MJ/L but better lubrication and complete combustion associated with the use of biodiesel compensates for this problem. Also biodiesel has almost no sulphur content and in turn is a much cleaner fuel. It is also used as an additive in ULSD( Ultra Low Sulfur Diesel).Biodiesel is also biodegradable and obtained from renewable sources. Also with upcoming research, new catalysts like SCRO-80 which speed up the transesterification process to the order of minutes instead of hours, facilitate greener biodiesel production and increase profits are coming into the market and innovations like these are fuelling the shift towards greener fuels.

The absence of sulfur in 100% biodiesel should extend the life of catalytic converters.

Biodiesel fuel can also be used in combination with heating oil to heat residential and industrial buildings. This can reduce dependence on non-renewable and increasingly expensive heating oil.

Biodiesel fuel can generally be used in existing oil heating systems and diesel engines without modification, and it can be distributed through existing diesel fuel pumps. This is an advantage over other alternative fuels, which can be expensive to use initially due to high cost of equipment modifications or new purchases. Biodiesel provides almost the same energy per gallon as petroleum diesel.

1.2.2.2 Disadvantages

Despite the fact that biodiesel is a very good alternative fuel, there are a few bad points associated with it. The first thing is that it undergoes cold gelling(solidification of the fuel at low temperature) and this creates problems when starting the engine in cold weather generally below -5oC. Another thing is the increased costs particularly in U.S owing to production from soybean which has less oil content of about 20%.But this can be overcome by using recycled cooking oil which is cheaper or by using seeds with a higher percentage oil content.

Biodiesel fuel can damage rubber hoses in some engines, particularly in cars built before 1994. You should check with the manufacturer before using biodiesel to see if you need to replace any hoses or rubber seals.

Biodiesel cleans the dirt from the engine. This dirt then collects in the fuel filter, which can clog it. Clogging occurs most often when biodiesel is first used after a period of operation with petroleum diesel, so filters should be changed after the first several hours of biodiesel use.

Biodiesel is not distributed as widely as traditional, petroleum diesel, but distribution infrastructure is improving.

.3 WHY MUSTARD OIL?

The oils generally in use as feedstock for biodiesel production are canola and soyabean, but mustard has numerous advantages starting with the fact that it is much cheaper to produce on a large scale basis.

Mustard oil has the advantage that it can be produced at a cheaper cost and also demands lesser investment in terms of pesticides, etc and has a good oil content. Also, processing required for mustard oil is far less than that required for other vegetable oils like canola for instance because of minimum suspended particulates.

Moreover, mustard oil is comparatively easier to produce since the suspended particulate matter in other vegetable oils like canola oil require more processing.

Mustard oil has a component called erucic acid which aids in lubrication and also has a lower melting point which is a plus point considering the cold gelling problem.

In the long run, biodiesel blends will help in reducing pollution especially Sox emissions and will burn cleaner and greener and in reducing dependence on conventional diesel.

Thus, by using mustard oil to make biodiesel we can use the byproduct or waste after extracting the oil also as a biodegradable pesticide.

CHAPTER 2

2.1 MAKING BIODIESEL

Transesterification is the basic process involved in biodiesel production. In transesterification, fats or vegetable oil reacts with an alcohol in the presence of a catalyst like caustic soda(alkali) to produce a mixture of fatty esters and glycerol. Usually, the esters produced have 5 carbon chains and the relative ratio of these decide the cetane number, cold flow, etc.

Figure 1: Transesterification

This reaction is industrially carried out as a batch process in small scale biodiesel plants whereas in large biodiesel plants, the process is carried out as a continuous process.

Biodiesel Preparation:

Take about 5g of NaOH and completely dissolve it in about 220 ml of CH3OH.

Heat 1 litre of mustard oil to about 60oC using a water bath.

Now pour the NaOH & CH3OH solution into the heated oil and keep stirring for about 10 minutes at 60 oC.

Now transfer the contents to a closed container & shake vigorously for about 5 minutes.

Now keep the container undisturbed for 2 days.

After 2 days, the glycerin solidifies, separates out and is collected at the bottom of the container and a mixture of fatty acid methyl esters and soap floats on top.

Slowly remove the top layer and transfer it to another container.

Now slowly add some warm distilled water so that the soap dissolves, forming a white soapy solution which is then separated. This step is called water washing.

Water washing should be done atleast 3 times to remove all the soap.

Leave the biodiesel in open air for about a day so that any remaining water evaporates.

Then, filter the biodiesel about 2-3 times, to remove any particulates.

Now the biodiesel is ready for use as fuel.

The above procedure was used to prepare a small batch of biodiesel. For large scale manufacture, only 80% of the alcohol is mixed initially and once the reaction is complete, the byproduct glycerol is separated. Then the rest of the alcohol and catalyst are mixed in the second reactor for better biodiesel yield. This method is advantageous because alcohol requirement is much lesser than in the case where only one reactor is used.

Now, the glycerol obtained is another high value product. Separation of glycerol and the ester mixture happens because of the low solubility of glycerol in esters. This separation is carried out in large scale manufacturing using settling tanks or centrifuges. The presence of methanol(alcohol) in the mixture reduces solubility of glycerol ,but it is not removed till the esters and glycerol are separated out in order to prevent the backward reaction from taking place. Once the transesterification is completed to an optimum level, then water may be added to improve separation of glycerol and biodiesel.

Figure 2: Schematic of Biodiesel production

The water washing step seen in the schematic above is the separation step. The concept here is that the water molecules attach themselves to the soap molecule and they fall out quickly. Once this glycerol is separated with multiple washes, the biodiesel will not be able to retain large quantities of water and thus pure biodiesel can be obtained in about 2 days. Thus water washing speeds up biodiesel production.

CHAPTER 3

Lab Experiment

3.1 Objective: To understand and analyze the performance of diesel engine using biodiesel as fuel

3.2 Aim: To determine:

Brake power (KW)

BSFC (%)

BTE (%)

Volumetric Efficiency (%)

3.3 Description:

Loading Arrangement:

Loading is done using the rope brake dynamometer, in which the dynamometer is coupled with the output shaft of the engine. Different loads were applied by turning the manual hand wheel which correspondingly increases the tension applied on the output shaft by the rope. There is a cooling water arrangement also provided.

Exhaust heat loss measurement:

For this purpose, water is made to flow in the outer jacket in the opposite direction as the exhaust gases at a specific flowrate and the temperature difference at water inlet and outlet is measured to calculate heat loss from exhaust. The cooling water flowrate is adjusted using a rotameter.

Fuel Input Measurement:

Fuel input is accurately measured with the flow sensors and all this information is processed by the computer.

3.4 Procedure:

Make sure that the specified engine oil( SAE 40) is used and topped up to the safe operation level.

Filter the biodiesel once more to ensure there are no particulates in the fuel mixture.

Diesel and biodiesel should be mixed as per the required composition of 5%, 10% and 15% by volume.

Fill the diesel tank with the fuel and connect the fuel line and engine.

Ensure that the fuel input valves are in open position and drain valves are closed.

Set the water flowrate to exhaust gas calorimeter to 200 LPH .

Open cooling water supply to rope brake dynamometer.

Lift the decompressing lever on both cylinders and rotate the flywheel quickly with the lever provided. Once a good speed is achieved, push both decompressing levers down and the engine starts.

After some time, when the engine stabilizes, gradually increase the load and run the test for 0kg, 8kg, 16kg and 24kg loads.

Record all observations.

Once the experiment is over, reduce the load to 0kg and then turn off the engine.

Drain out all the fuel left in the fuel tank before using the next biodiesel mixture with the drain valves provided at the fuel tank and at the fuel supply line.

Once all the runs are complete, close the fuel and cooling water line.

Engine Specifications:

Engine: Two cylinder, 4stroke, water cooled direct injection diesel engine

Horsepower Rating: 14 HP

Bore: 87.5 mm

Stroke length: 110 mm

Brand: Kirloskar

3.5 Formulae:

1) Brake Power:

T = (m x g x R) Nm

BP = (2Ï€NT)/( 60 x 1000) KW

2) Fuel consumed by engine:

Qf = (Xf x ρf)/(T x 106) Kg/s

3) Brake Specific Fuel Consumption:

BSFC = (Qf/BP) Kg/KWs

4) Input Power or Heat supplied by fuel:

Hf = Qf x CV KW

5) Brake Thermal efficiency:

η BTE = (BP/ Hf) x 100 %

6) Volumetric efficiency:

η vol = (Qa/Vs) x 100 %

3.6 Observation:

100% Diesel

ρf = 804 kg/m3 CV = 45300 KJ/Kg

Table 1

S.No

1

2

3

4

RPM ,N

1498

1498

1498

1498

Load acting on dynamometer ,m (kg)

0

8

16

24

Volume of fuel consumed ,X(ml)

50

50

50

50

Time taken to consume X ml of fuel , T(s)

147.25

111.61

85.98

76.34

Air Flowrate (Qa)

1.62 x 10-2

1.57 x 10-2

1.57 x 10-2

1.537 x 10-2

5% Biodiesel & 95% Diesel

ρf = 806.8kg/m3 CV = 44885 KJ/Kg

Table 2

S.No

1

2

3

4

RPM (N)

1498

1498

1498

1498

Load acting on dynamometer ,m (kg)

0

8

16

24

Volume of fuel consumed ,X(ml)

50

50

50

50

Time taken to consume X ml of fuel , T(s)

133

106.10

95.75

87.54

Air Flowrate (Qa)

1.59 x 10-2

1.579 x 10-2

1.559 x 10-2

1.539 x 10-2

10% Biodiesel & 90% Diesel

ρf = 809.6 kg/m3 CV = 44470 KJ/Kg

Table 3

S.No

1

2

3

4

RPM (N)

1498

1498

1498

1498

Load acting on dynamometer ,m (kg)

0

8

16

24

Volume of fuel consumed ,X(ml)

50

50

50

50

Time taken to consume X ml of fuel , T(s)

144

104.5

96.91

89.43

Air Flowrate (Qa)

1..58 x 10-2

1.572 x 10-2

1.549 x 10-2

1.53 x 10-2

15% Biodiesel & 85% Diesel

ρf = 812.4 kg/m3 CV = 44055 KJ/Kg

Table 4

S.No

1

2

3

4

RPM (N)

1498

1498

1498

1498

Load acting on dynamometer ,m (kg)

0

8

16

24

Volume of fuel consumed ,X(ml)

50

50

50

50

Time taken to consume X ml of fuel , T(s)

157.10

114.6

99.6

91.20

Air Flowrate (Qa)

1.58 x 10-2

1.56 x 10-2

1.56 x 10-2

1.54 x 10-2

3.7 Calculation Table:

100 % Diesel

Table 5

Load ,m (kg)

0

8

16

24

T(Nm)

0.647

12.94

25.89

38.847

N(RPM)

1498

1498

1498

1498

BP(KW)

0.1014

2.029

4.058

6.087

T(sec)

147.25

111.61

85.98

76.34

Qf(kg/s)

2.73 x 10-4

3.602 x 10-4

4.675 x 10-4

5.132 x 10-4

BSFC(kg/KWs)

2.692 x 10-3

1.775 x 10-4

1.152 x 10-4

8.43 x 10-5

Hf(KW)

12.37

16.317

21.18

23.24

BTE(%)

0.82

12.435

19.161

26.19

5% Biodiesel & 95% Diesel

Table 6

Load ,m (kg)

0

8

16

24

T(Nm)

0.647

12.94

25.89

38.847

N(RPM)

1498

1498

1498

1498

BP(KW)

0.1014

2.029

4.058

6.087

T(sec)

133

106.10

95.75

87.54

Qf(kg/s)

3.032 x 10-4

3.802 x 10-4

4.213 x 10-4

4.608 x 10-4

BSFC(kg/KWs)

2.99 x 10-3

1.873 x 10-4

1.038 x 10-4

7.5702 x 10-5

Hf(KW)

13.609

17.06

18.91

20.68

BTE(%)

0.745

11.89

21.459

29.43

10% Biodiesel & 90% Diesel

Table 7

Load ,m (kg)

0

8

16

24

T(Nm)

0.647

12.94

25.89

38.847

N(RPM)

1498

1498

1498

1498

BP(KW)

0.1014

2.029

4.058

6.087

T(sec)

144

104.5

96.91

89.43

Qf(kg/s)

2.81 x 10-4

3.873 x 10-4

4.177 x 10-4

4.526 x 10-4

BSFC(kg/KWs)

2.7712 x 10-3

1.9088 x 10-4

1.029 x 10-4

7.4355 x 10-5

Hf(KW)

12.496

17.22

18.575

20.127

BTE(%)

0.8114

11.78

21.846

30.24

15% Biodiesel & 85% Diesel

Table 8

Load ,m (kg)

0

8

16

24

T(Nm)

0.647

12.94

25.89

38.847

N(RPM)

1498

1498

1498

1498

BP(KW)

0.1014

2.029

4.058

6.087

T(sec)

157.10

114.6

99.6

91.20

Qf(kg/s)

2.585 x 10-4

3.545 x 10-4

4.0754 x 10-4

4.453 x 10-4

BSFC(kg/KWs)

2.549 x 10-3

1.747 x 10-4

1.0041 x 10-4

7.3155 x 10-5

Hf(KW)

11.388

15.617

17.952

19.617

BTE(%)

0.8904

12.99

22.604

31.029

Sample Calculation:

For 5% Biodiesel, 8kg load

T = m x g x R

= 8 x 9.81 x 0.165

=12.94 Nm

BP = (2Ï€NT)/( 60 x 1000)

= (2 x π x 1498 x 12.94)/( 60 x 1000)

= 2.029 KW

Qf = (Xf x ρf)/(T x 106)

= (50 x 806.8) / (106.10 x 106)

= 3.802 x 10-4 kg/s

BSFC = (Qf/BP)

= (3.802 x 10-4/ 2.029)

= 1.873 x 10-4 Kg/KWs

Hf = Qf x CV KW

= 3.802 x 10-4 x 44885

= 17.06 KW

η BTE = (BP/ Hf) x 100 %

= (2.029/ 17.06) x 100

= 11.89 %

η vol = (Qa/Vs) x 100 %

= (1.579 x 10-2 / 0.0165) x 100

= 95.75%

CHAPTER 4

GRAPHICAL ANALYSIS

4.1 BSFC VS LOAD

100 % Diesel ( Baseline)

Figure 1

5% Biodiesel & 95% Diesel

Figure 2

10% Biodiesel & 90% Diesel

Figure 3

15% Biodiesel & 85% Diesel

Figure 4

Comparison of BSFC for all % compositions tested

Figure 5

4.2 Brake Power VS Load

Figure 6

4.3 Volumetric Efficiency VS Load

Figure 7

4.4 BTE VS LOAD

100 % Diesel ( Baseline)

Figure 1

5% Biodiesel & 95% Duesel

Figure 2

10% Biodiesel & 90% Diesel

Figure 3

15% Biodiesel & 85% Diesel

Figure 4

BTE Comparison for all % compositions of Biodiesel

Figure 5

CHAPTER 5

RESULTS

Load tests were carried out keeping the engine rpm constant at about 1500 rpm. The performance tests were carried out using pure Diesel, 5% Biodiesel & 95% Diesel, 10% Biodiesel & 90% Diesel and finally 15% Biodiesel & 85% Diesel under various loading conditions of no load, 8kg, 16 kg & 24 kg. The results obtained were plotted as above and analyzed.

BSFC comparison for all % compositions

Figure 6

Here, we see that as load increases, the BSFC is decreasing. This shows that as more brake power is produced, correspondingly more fuel is being consumed. The reason for reduction in BSFC when biodiesel blends are used is that atomization is affected owing to higher viscosity and surface tension of the biodiesel

BTE comparison for all % compositions of Biodiesel

Figure 13

Here, we see that with increasing load, the brake thermal efficiency also increases as brake power output is more. Biodiesel blends have higher brake thermal efficiency because of the oxygen content in biodiesel and hence better fuel burn characteristics.

CHAPTER 6

CONCLUSIONS

Biodiesel has quite a few advantages including the fact that it is renewable, has higher cetane number, less polluting in terms of SOx emissions because of negligible sulfur content. Even CO2 levels produced when running diesel engines on biodiesel are lesser than those produced when running them on petrodiesel.

The bad side is that owing to higher viscosity, higher surface tension, fuel atomization is affected. Another disadvantage is that when it is used for the first time, it cleans out all the dirt left from previous petrodiesel use and this can accumulate in the fuel filter and so, the fuel filter may need to be replaced.

Studies indicate that biodiesel blends upto 20% can be used to run compression ignition engines without any modifications, but generally in EU countries only B5 or 5% biodiesel and 95% diesel mixtures have been approved for use in diesel vehicles. This is because NOx emissions increase with higher biodiesel blends while for B5, the rise in these emissions is very negligible and hence is recommended.

CHAPTER 7

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