Influence of Fatty Acid Composition on Performance ...

Proceedings of the APAS (Golden Jubilee) Science Congress November 13-15, 2014, CSIR-IICT, Hyderabad

Influence of Fatty Acid Composition on Performance, Combustion and Exhaust Emissions Characteristics of a Bio-Diesel Engine *P V Rao1, Jaedaa Abdulhamid2 and K S S Sindhura3 1Associate

Professor in Mechanical Engineering, 2Post-Graduation Student in Marine Engineering, 3Post-Graduation Student in Mechanical Engineering Andhra University, Visakhapatnam-530 003, Andhra Pradesh

*E-mail: [email protected]

Abstract: The present work discuss the influence of fatty acid composition of biodiesel fuels (methyl esters) on diesel engine performance, combustion, and exhaust emission characteristics. Two biodiesel fuels, namely: cotton seed and coconut are prepared in the laboratory and were characterized before testing in a single cylinder diesel engine. It is observed that, the kinematic viscosity, density, and iodine value of cotton seed methyl ester is more than that of coconut methyl ester, where as the cetane number of cotton seed methyl ester is less than that of coconut methyl ester. From the engine experiments, it is observed that, the performance of a coconut biodiesel is superior to cotton seed biodiesel. It is also observed that, the exhaust emissions such as HC, CO2, CO, Soot and NOx of a cotton seed biodiesel engine is more than that of coconut biodiesel. These higher levels of exhaust emissions (particularly NOx) of cotton seed biodiesel is attributed to the presence of unsaturated fatty acids (C18:1 and C18:2), lower cetane number and higher iodine value, as compared to that of coconut biodiesel.

1. Introduction: Diesel engines are the most efficient prime movers and these engines use petro diesel as a fuel. Petro diesel keeps the world moving. Diesel fuel plays a vital role in the nation’s economy and standard of living. The major uses of the petro diesel fuel are: on-road transportation, agriculture, rail transportation, marine shipping, electric power generation, military transportation, mining, and construction, etc. It is well known that fossil fuels will be depleted in near future, and their combustion has led to environmental problems and global climate change. In order to alter this trend and to save the planet earth, much effort is needed to develop new fuel technologies and to find alternative energy sources [1-3]. Vegetable oils like coconut oil and cotton seed oil, consists of hydrocarbons called triglycerides. The triglyceride composition is unique for every plant oil. Two biodiesel fuels namely: coconut and cotton seed biodiesel fuels were considered in this work. These fuels are prepared from their respective raw vegetable oils through two-stage transesterification. All biodiesels have excellent lubricity and high oxygen content including the coconut biodiesel. However, the added features of high solvency, high cetane number, and excellent distillation range are specific only to coconut biodiesel due to presence of carbon 8, 10, 12 and 14 apart from carbon 16 and18, which are typical profile of most biodiesels [4]. Previous studies have shown that, the higher bulk modulus of BD fuel appears to cause injection timing to advance. A fuel that is less compressible, such as BD, will inject prematurely. It takes less time for the pressure pulses to travel from the fuel pump to the injector. This

Contributed Oral Presentations (COP-13)-Engineering Sciences (ES-IV)

Proceedings of the APAS (Golden Jubilee) Science Congress November 13-15, 2014, CSIR-IICT, Hyderabad tendency contributes to some but not all of the increase in NOx emission [5, 6]. The physical and chemical properties of these biodiesel fuels were tabulated the following Table 1:

Table 1: Physicochemical properties of coconut and cotton seed biodiesel fuels [7 and 8] PetroCoconut Cotton Seed ASTM Property Units Diesel Biodiesel Biodiesel D6751-02 Carbon Chain Kinematic Viscosity Density Iodine Value Cetane Number Flash Point Temp. Pour Point Temp. Molecular Weight Acid Value Carbon Residue Calorific Value Bulk Modulus Adiabatic Flame Temp. Molecular Formula Saturation

Cn cSt @40 oC g/cm3 g I2/100 g --------oC oC g/mol mg KOH/g wt.% MJ/kg MPa@200bar Kelvin CHO %

HC:C8-C32 2.25 0.825 38 49 70 -20 226 0.35 0.1 42.5 1425 --------C18H36 40

FAME: C6-C18 3.25 0.858 10 65 110 0 222 0.22 0.01 35.93 1418 2277 C13H27O2 90

FAME: C14-C20 5.8 0.895 110 52 162 -5 284 0.5 0.03 39.65 1551 2361 C18H34O2 38

C12-C22 1.9-6.0 870-900 120 max. 47 min. 130 min. -15 to 16 292 0.8 0.05 ------------------------------------

2. Experimentation: The experiments were carried out on a naturally aspirated, vertical-type, stationary, 4-stroke cycle, single cylinder, Diesel engine with the following specifications as shown in Table 2. The experimental test rig is shown in the Figure 1. The fuel injection of the engine was performed at a static injection timing (optimum) of 230 bTDC set for petro-diesel fuel. Table 3 shows the specifications of the gas analyzer (AVL 444) used for the measurement of engine exhaust emissions. Table 2: Specifications of diesel engine test rig model: Kirloskar- TV1 Parameter Units Value Type of Engine Rated Power Bore x Stroke Connecting Rod Length Compression Ratio Fuel Injection System Injection Timing Injection pressure

-----kW @RPM mm x mm mm -----Degrees bar

Four-Stroke and Diesel 3.52 @1500 87.5x 110 234 17.5 In-Line and Direct Injection 23 b TDC 220

Table 3: Specification of the Exhaust Gas Analyzer Emissions Measuring Range Accuracy Carbon Monoxide (CO) Carbon Dioxide (CO2) Hydro Carbons (HC) Oxides of Nitrogen (NOx) Oxygen (O2) Lambda

0-10 % volume 0-20% volume 0-2000 ppm 0-5000 ppm 0-22 % volume 0-9.99


0.03% 0.5 % 0.01 % 1% 0.01 % 0.001 %


Figure 1: Experimental Test Rig: Diesel Engine setup and Exhaust Gas Analyzer

3. Results and Discussion: The performance of the engine is presented in terms of brake thermal efficiency (BTE), mechanical efficiency (ME), indicated mean effective pressure (IMEP), and brake specific fuel consumption (BSFC) as shown in the following Figures: 75 65

30

55

BT E (%)

M E (%)

35

DIESEL BIODIESEL

45 35

25 20 DIESEL BIODIESEL

15

25

10

15 0.5

1

1.5

2

2.5

3

3.5

0.5

1.5

2

2.5

3

3.5

Brake Power (kW)

Brake Power (kW)

Figure 2: Mechanical Efficiency

1

Figure 3: Brake Thermal Efficiency

From the Figure 2, it is observed that the mechanical efficiency is less in case of biodiesel as compared to that of petro diesel at each brake power values. The maximum percentage of decrement in mechanical efficiency of biodiesel relative to diesel is -8.12% and from the Figure 3, it is observed that the percentage of decrement in thermal efficiency of biodiesel relative to petro diesel is -11.58%.



6.5

0.8

6

0.7

B S F C (kg/kWH)

I M E P (bar)

From the Figure 4, it is observed that the IMEP is more in case of biodiesel and the percentage of increase in IMEP of biodiesel relative to petro diesel is 10.12%. It is also observed that the BSFC is more in case of biodiesel and the percentage of increase in BSFC of biodiesel relative to petrodiesel is 14.18%, as shown in Figure 5.

5.5 5 4.5 4

DIESEL

3.5

BIODIESEL

3

DIESEL BIODIESEL

0.6 0.5 0.4 0.3 0.2

0.5

1

1.5

2

2.5

3

3.5

0.5

1.2

Brake Power (kW)

1.9

2.6

3.3

4

Brake Power (kW)

Figure 4: Indicated Mean Effective Pressure

Figure 5: Brake Specific Fuel Consumption

The exhaust emissions were measured for diesel and biodiesel at different values of brake power and the values were compared as shown in the following Figures: From the Figure 6, it is observed that the CO volume percentage values were measured for diesel and biodiesel at different values of brake power and the values were compared. At 3.5 kW, the CO levels are 0.025% for petro diesel and 0.045% for biodiesel. Also the HC emissions were 35 ppm for petro diesel and 19 ppm for biodiesel as shown in Figure 7. 40

DIESEL

0.06

BIODIESEL

0.05 0.04

HC (ppm)

CO (%)

0.07

DIESEL

35

BIODIESEL

30 25 20

0.03

15

0.02

10 0.5

1

1.5

2

2.5

3

3.5

Brake Power (kW)

Figure 6: Carbon Monoxide Emission

0.5

1

1.5

2

2.5

3

3.5

4

Brake Power (kW)

Figure 7: Hydro Carbon Emissions

From the Figure 8, it is observed that, the NOx emissions increases as the output increases. At 3.53 kW, NOx emissions were 35 ppm for petrodiesel and 19 ppm for biodiesel. The increase in NOx is attributed to the high adiabatic flame temperature of the biodiesel fuel. Figure 9 shows that, the smoke opacity of biodiesel is less than that of petro diesel and the opacity is 4.30% for


Proceedings of the APAS (Golden Jubilee) Science Congress November 13-15, 2014, CSIR-IICT, Hyderabad petrodiesel and 2.90% for biodiesel. This is due to the presence of 11% oxygen in biodiesel which leads to improved burning of the biodiesel.

1200

5%

NOx (ppm)

1000

Smoke Opacity (%)

DIESEL BIODIESEL

800 600 400

DIESEL

4%

BIODIESEL

3% 2% 1% 0%

200 0.5

1

1.5 2 2.5 3 3.5 Brake Power (kW)

4

0.5

1

1.5

2

2.5

3

3.5

4

Brake Power (kW)

Figure 8: Oxides of Nitrogen Emissions

Figure 9: Smoke (Soot) Opacity

4. Conclusions: The following conclusions were made from the results:     

Indicated mean effective pressure of cotton seed biodiesel is 10.12% higher than that of petrodiesel. Brake specific fuel consumption (BSFC) of cotton seed biodiesel is 14.18% higher than that of petrodiesel. Significant reduction in carbon monoxide, unburned hydrocarbon and smoke opacity were observed for cottonseed biodiesel as compared to that of petrodiesel. There is a slight increase in NOx for cotton seed biodiesel when compared to diesel fuel. This is due to higher oxygen content of biodiesel which will form oxides of nitrogen at high combustion temperatures. Higher levels of NOx emissions of cotton seed biodiesel is attributed to the presence of unsaturated fatty acids (C18:1 and C18:2) and lower cetane number

References: [1] Biodiesel, Documentation of the World-Wide Status 1997, Austrian Boifuels institute, ABI, Austria. [2] Korizi, A., 1995, “The Perspectives of Biodiesel Development in Greece.” Diploma thesis, Laboratory of Fuel Technology and Lubricants, National Technical University of Athens, Greece [3] “Acute Toxicity of Biodiesel to Freshwater and Marine Organisms,” 1996, Development of Rapeseed Biodiesel for Use in High-Speed Diesel Engines. [4] Refael S. Diaz, Coconut for Clean Air, Asian Institute of Petroleum Studies, Inc. (AIPSI), Manila, Philippines [5] Tat, M.E., J.H. Van Gerpen, S. Soylu, M. Canakci, A.Monyem, and S. Wormley, “The Speed of Sound and Isentropic Bulk Modulus of Biodiesel at 21 degrees C from Atmospheric Pressure to 35 MPa.” Journal of the American Oil Chemists Society, 2000, 77(3): p. 285-289. [6] Monyem, A., J.H. Van Gerpen, and M. Canakci, “The Effect of Timing and Oxidation on Emissions from Biodiesel-Fueled Engines”. Transactions of the ASAE, 2001, 44(1):p.35-42


Proceedings of the APAS (Golden Jubilee) Science Congress November 13-15, 2014, CSIR-IICT, Hyderabad [7] American Society for Testing and Materials, Standard Specification for Biodiesel Fuel (B100) Blend Stock for distillate Fuels, designation D6751-02, ASTM International, West Conshohocken, PA (2002) [8] Rao, V. Pulagala and Rao, Basava V. A.” Influence of Physical and Chemical Properties of Two Biodiesel Fuels on Performance, Combustion, and Exhaust Emission Characteristics in a DI-CI Engine” Proceedings of the ASME Internal Combustion Engine Division 2008 Spring Technical Conference’ ICES2008, April 27-30, 2008, Chicago, Illinois, USA
