Biodiesel Characterization and Influence of its

The Seventh International Conference on Modeling and Diagnostics for Advanced Engine Systems (COMODIA 2008), July 28-31, 2008, Sapporo, Japan

FL2-4  



   



     

 





                                                                                                                                                                                                                                                                                                                                                               



 Copyright © 2008 by the Japan Society of Mechanical Engineers

-807-

The Seventh International Conference on Modeling and Diagnostics for Advanced Engine Systems (COMODIA 2008), July 28-31, 2008, Hokkaido, Japan (99% pure) and acid catalyst (sulfuric acid-98% pure) in one hour reaction at 55 0C. In the second stage, the triglyceride portion of the vegetable oil reacts with methanol and base catalyst (potassium hydroxide-99% pure), in one hour reaction at 65 0C, to form ester and glycerol. The raw fatty acid methyl ester is then purified by the process of water washing with airbubbling. The biodiesel produced from rice bran oil is known as rice bran oil methyl ester (ROME). Measurements of properties were carried out according to ASTM standards and their values are presented in the tables 1, and 2. From the testing of the ROME, it is observed that, the properties are meeting the specifications of biodiesel standards of the ASTM D6751-02 “Standard Specification for Biodiesel Fuel (B100) Blend Stock for Distillate Fuels” [8]. And the above ROME was found suitable for usage as biodiesel.

(NO2) at low temperatures in the presence of oxygen. The sum of NO and NO2 is called NOx. The formation of NOx is dependent on the temperatures during the combustion, the amount of oxygen (O2) and nitrogen (N2) in the charge and the time available for them to react with each other in the combustion chamber. NOx and HC’s are the precursor pollutants which can combine to form photochemical smog. These irritate the eyes and throat, reduces the ability of blood to carry oxygen to the brain and can cause headaches, and pass deep into the lungs causing respiratory problems for the human beings. Long-term exposure has been linked with leukemia. The major challenge for the existing and future diesel engines is meeting the very tough emission targets at affordable cost, while improving fuel economy. The focus on NOx, CO and HC reductions to meet stringent emission norm ‘EURO 5’ may represent a major hurdle. Moreover, the usage of low sulfur will be mandatory in the future. Different methods are being used to reduce these emissions from the diesel engines. One is improving the engine technology and the other is using of alternate or oxygenated fuels to increase combustion efficiency. Over the past several years, there has been increased interest in alternative diesel fuels to control exhaust emissions and to provide energy security. Therefore, from the point of view of protecting our surrounding environment, human health and concerns for long-term energy security, it becomes necessary to develop alternate fuels with properties comparable to petroleum diesel (PD) fuel. Vegetable oil is one such source. Vegetable oils have comparable properties with PD fuel. Using straight vegetable oil lead to the clogging of the fuel injectors and there is a problem of starting especially when the engine is cold. Also, emissions of CO, HC, and oxides of sulfur (SOx) were found higher. To avoid these problems, the straight vegetable oils can be chemically treated to enhance its properties, after which the vegetable oil is known as biodiesel (BD). The BD is often referred to as fatty acid methyl ester (FAME). The biodiesel derived from rice (Oryza sativa) bran oil was used in this study. The oil extracted from the rice-bran has high free fatty acids content [2]. The experiments are conducted on a direct injection (DI) diesel engine to find the influence of properties of the biodiesel on the combustion and emission characteristics. Previous studies have shown that, the higher bulk modulus of BD fuel appears to cause injection timing to advance. This tendency contributes to some but not all of the increase in NO emission [3, and 4].

BIODIESEL PREPARATION CHARACTERIZATION

PHYSICAL, CHEMICAL THERMODYNAMIC PROPERTIES

AND

The feed stock dependent fatty acid compositions (hydrocarbon chains) of ROME vary from ‘C14 to C20’, with the long chain oleic acid (18:1) and linoleic acids (18:2) are the highest. The amount of oleic acid is 42.05% and the linoleic acid is 36.36%. The ROME mainly consists of long chain mono (43%) and poly (38%) unsaturated fatty acids as shown in table (1). The ROME contains 19% saturated acids only. The carbon chain of PD fuel includes both medium (C8-C12) and long (C14-C32) carbon chain (see figure 1). The hydrocarbons in PD fuel range in size from 8 carbon atoms per molecule to 32 carbon atoms per molecule. The peak in the carbon-number distribution occurs at about 13 to 19 carbon atoms per molecule, as shown in figure 1. Table 1: Percentage of Saturated and Unsaturated Fatty Acids of ROME [9, 10, and 11] Saturated Unsaturated Long Chain Mono-Unsaturated Poly-Unsaturated Fatty Acids Fatty Acids Fatty Acids (14:0, 16:0, (MUFA) (PUFA) 18:0, 20:0) (16:1,18:1,20:1) (18:2, 18:3) 19 43 38 PD fuel typically contains over 400 distinct types of organic compounds. PD fuel composed of saturated hydrocarbons (primarily paraffin’s-the straight chain HC’s) and aromatic hydrocarbons (naphthalene’s-the cyclic HC’s and alkylbenzenes). Approximately 80 % (vol.) of the fuel contains alkanes, with the remainder (i.e. 20%) comprised of aromatic molecules. Typical PD fuel contains approximately 44% of n-Paraffin, 29% of i-Paraffin and 7% of Naphthene. The aromatics include polycyclic aromatic compounds containing 2, 3, 4, and 5 fused benzene rings. The aromatics containing multiple benzene rings are known as poly-aromatic hydrocarbons (PAHs). The

AND

The BD fuel is produced by chemically reacting oil with an alcohol (methyl), in the presence of a catalyst. A two-stage process [5, 6, and 7] is used for the esterification of the rice bran oil. The first stage of the process is to reduce the FFA (Free Fatty Acids) content in vegetable oil by esterification with methanol

2 -808-

The Seventh International Conference on Modeling and Diagnostics for Advanced Engine Systems (COMODIA 2008), July 28-31, 2008, Hokkaido, Japan Table 2: Physical, Chemical and Thermodynamic Properties of PD and ROME Fuels used for Testing Property PD ROME ASTM D 6751-02

aromatic benzene rings of the polycyclic hydrocarbons acts as nuclei for growth of undesired soot. 80

(Biodiesel)

Mass (%)

70 60

ROME

50

PD

Carbon Chain Cn *C Carbon O (C) % M Hydrogen P (H ) % O Nitrogen S (N) % I Sulfur T (S) % I Oxygen O (O ) % N C/H ratio Chemical Formula Molecular Weight (g/mol) *Bulk Modulus (bar) Stoichiometric A/F Ratio **LCV (kJ/kg) **Cetane Number ***Iodine Value Carbon Residue (Wt. %) Acid Number (mg KOH/g) Viscosity (cSt @ 40 oC) Specific Gravity @15 0C Flash Point (oC) Fire Point (oC) Pour Point (oC) Cloud Point(oC) Color

40 30 20 10

C32

C30

C26

C28

C22

Carbon Number

C24

C18

C20

C14 C16

C8 C10 C12

0

Figure 1: Typical Carbon Number Distribution of Fuels The fuel elements of primary interest to diesel engine combustion are carbon (C), hydrogen (H2), oxygen (O2) and sulfur (S). The amount of each of these elements determines the fuel composition, while the location and type of bond making up the fuel molecules determines the fuel structure. The PD fuel made up of a mixture of various hydrocarbon molecules and contain little oxygen and very small amount of sulfur, while the biodiesel fuel consists of three basic elements namely: carbon, hydrogen and significant amount of oxygen. The amount of oxygen present in the ROME is 9.43% as compared to up to 1% in PD fuel, as shown in the table 2. The increases of O2 in biodiesel is related to the reduction of C and H2, causes the lower value of lower calorific values (LCV) of the biodiesel as compared to that of PD fuel, because O2 is ballast in fuel and ‘C and H2' are the sources of thermal energy. Since the calorific value is directly related to elemental composition of the fuel. The LCV of methyl ester is lower than PD fuel because of oxygen [12] and the biodiesel consists of esters of fatty acids with a different degree of saturation. The biodiesel has lower volumetric heating values (about 10%) than PD fuel. The stoichiometric air-fuel ratio of biodiesel (see table 2) will be lower than PD fuel because of O2 is present in the biodiesel, as a result the combustion efficiency of the BD fuel will be increased [13, and 14]. The quantity of nitrogen (N2) present in the biodiesel fuel is also shown in the table 2. The ignition quality of the fuel is measured by cetane number (CN) and it measures how easily ignition occurs. The CN assists in smooth combustion with lower knocking characteristics in diesel engines. The CN requirement for the engine depends on the design, size, speed, and load. Diesel engines that are run on low cetane fuels will suffer from excessive CO, HC, PM and smoke emissions, especially at low load and low temperature operations.

HC (C8-C32) 86.25

FAME (C14-C20) 77.83

FAME (C12-C22) 77

12.5

11.76

12

0

0.98

----

0.25

0

0.05

1.0

9.43

11

6.9 C16 H34

6.61 C93H167NO9

---------

226

274

292

15 000

19 000

-----

14.86

13.87

13.8

42 500 48

38 552 58

37 518 48-70

38

100

60-135

0.1

0.04

0.05

0.35

0.46

0.8

2.2

4.5

1.9-6.0

0.82

0.87

0.87-0.89

66 72 -20 -4

153 160 -9 -----

100-170 -------15 to 16 -3 to 12

-----Light Brown Green Appearance Clear Clear ----Note:*Tests were conducted at the Indian Institute of Chemical Technology (IICT), Hyderabad, India **Tests were conducted by Hindustan Petroleum Corporation Limited (HPCL), Visakhapatnam, India. *** Test was conducted by Department of In-organic and Analytical Chemistry, Andhra University, Visakhapatnam, India. The CN for ROME is 58 and for PD fuel is 48 (see table 2). The iodine value (IV) shows the level of un-saturation of the fuel, which means, higher the percentage of unsaturation, larger will be the iodine

3 -809-

The Seventh International Conference on Modeling and Diagnostics for Advanced Engine Systems (COMODIA 2008), July 28-31, 2008, Hokkaido, Japan

3.72 kW). The engine is tested with baseline PD fuel, and ROME. This engine is also tested with the preheated ROME (i.e. ROME_H); to find the influence of reduced viscosity on all above characteristics. And for preheating the ester; a heating device was placed on the high pressure tube connecting the fuel-pump and the injector. The engine is allowed to warm up, until the cooling water temperature reaches a steady state of 80 0C. A computer interfaced piezoelectric sensor of range 0-145 bar was used to record the in cylinder pressure. Apex innovations, Pune, India, software: C7112 is used to record the combustion pressure in the cylinder. Pressure signals were obtained using data acquisition system. The average pressure data from 20 consecutive cycles were used for calculating combustion pressure parameters. The net HRR and cumulative heat releases were calculated from the acquired data.

value [15]. The ROME with 19% saturates has an iodine value of 100; while the PD with 40% of saturates has an iodine value of 38 (see table: 2). 7 PD

Kinematic Viscosity (cSt)

6

ROME

5 4 3 2 1 0 25

30

35 40 45 50 55 Temperature (deg. C)

60

Table 3: Test Engine Specifications Engine Make and Model Kirloskar (India), AV1 Maximum Power Output 3.72 kW Rated Speed (constant) 1500 Bore x Stroke 80 mm x 110 mm Compression Ratio 16.5 Fuel Injection System In-Line, Direct Injection Nozzle Opening Pressure 205 bar Method of Cooling Water cooled BMEP @1500 rpm 5.42 kg/cm2

65

Figure 2: Temperature versus Kinematic Viscosity for PD and ROME. The viscosity influences the injection characteristics (spray pattern and depth of penetration) of the fuel, and the quality of filtering. Viscosity of the fuel decreases with the increase of temperature, which in turn decreases the emissions of non-combusted products. Biodiesel usually has a higher viscosity than PD fuel [15]. The viscosity of PD and ROME at 30 0C is 3.0 and 5.7 cSt respectively, as shown in figure 2. The higher viscosities of biodiesel reduces the leakage of fuel in the plunger and barrel pair of the fuel pump [12] and minimum viscosity limits are imposed to prevent the fuel from causing wear in the fuel injection pump. The viscosity of preheated ROME at 60 0C (i.e. ROME_H) is equal to that of PD fuel at engine room temperature of 30 0C (see figure 2). The density of biodiesel is more than that of PD fuel and this compensates their lower value of calorific value. For this ester, the density (or specific gravity) is lower than that of water and their viscosity is low enough to allow ‘pump-ability’ (see table 2). The higher value of flash point belongs to biodiesel, because the biodiesel do not have the light fractions. The safety of the biodiesel is ensured due to higher flash point temperature.

EXPERIMENTAL PROCEDURE

SETUP

RESULTS AND DISCUSSIONS Combustion Analysis: Figure 3 shows the variation of peak pressures of PD and BD fuel with respect to brake power output. It is also observed that, the biodiesel is burning close to top dead center (TDC) (see figure 4) and their peak pressures are higher than that of PD fuel; even though the biodiesel is having lower value of LCV. The reason is attributed to the higher bulk modulus of the ROME. When, a high density (or high bulk modulus) fuel is injected, the pressure wave travels faster from pump end to nozzle end, through a high pressure in-line tube. This causes early lift of needle in the nozzle, causing advanced injection. Hence, the combustion takes place very close to TDC and peak pressures are increases due to existence of smaller cylinder volume. When the engine is running on ROME_H, the injection is slightly delayed. This is due to decrease in bulk modulus of biodiesel with increasing fuel temperature. It is also observed that, there is a reduction in peak pressures of ROME_H, as compared to that of ROME (see figure 3). The reason is attributed to early burning of ROME_H due to its faster evaporation at its high temperature (60 0C), which leads to reduction in its ignition delay. It is also observed that the rate of pressure rise is also reduced with the ROME_H (see figure 5).

AND

The experiments were carried out on a naturally aspirated, 4-stroke cycle, single cylinder; DI diesel engine with the following specifications is shown in table 3. The fuel injection was performed at a static injection timing (optimum) of 230 BTDC for PD fuel. Eddy current dynamometer is used to measure the power (or torque). Engine brake load was varied in five steps, ranging from 0% to 100% of the full load brake power output of 3.72 kW (i.e. at 0, 0.93, 1.86, 2.79 and

4 -810-

The Seventh International Conference on Modeling and Diagnostics for Advanced Engine Systems (COMODIA 2008), July 28-31, 2008, Hokkaido, Japan the cylinder pressure rises, entering into the premixed combustion phase. The premixed (or rapid) combustion is large with ROME than that of PD fuel (see figure 6 and 7). The reason is attributed to the combined effect of advanced injection and lower value of heat rejection, which occurs due to prevalence of smaller cylinder volume (or surface area) near the TDC.

70 PD Peak Pressure (bar)

65 60

ROME ROME_H

55 50

95

45 40 0.93

1.86

2.79

3.72

Net HRR (J/deg.)

0

Power (kW)

Figure 3: Variation of Peak Cylinder Pressure

85

PD

75

ROME

65

ROME_H

55 45 35 25 15 5

10

Crank Angle (degree)

9 8

-5 355 360 365 370 375 380 385 390 395 400 405

PD ROME

Crank Angle (degrees)

ROME_H

Figure 6: Variation of Net Heat Release Rate

7 6 5

100

4

PD

90

3

ROME

80 0

0.93

1.86

2.79

Peak HRR (net) (J/deg)

2 3.72

Power (kW)

Figure 4: Crank Angle for Peak Cylinder Pressure

ROME_H

70 60 50

Rate of Pressure Rise (bar/deg)

9

40

PD 30

8

ROME

7

ROME_H

0

0.93

1.86

2.79

3.72

Power (kW)

6

Figure 7: Variation of Peak HRR (net)

5 4

A noticeable change in combustion phases were observed between ROME and ROME_H (see figure 6). The peak value of premixed combustion was more for ROME, than that of ROME_H. And the diffusive combustion phase was more for ROME_H, than that of ROME. This is due to poor mixing of high viscosity (5.7cSt) ROME with the surrounding air. However, at the time of ignition, less quantity of airfuel mixture is prepared for combustion with preheated ROME. This is due to faster evaporation of the ROME_H. Therefore, more burning occurs in the diffusion phase rather than premixed phase. The increase in diffusive combustion is mainly due to

3 2 0

0.93

1.86

2.79

3.72

Power (kW)

Figure 5: Variation of Maximum Rate of Pressure Rise The peak pressure mainly depends on the combustion rate in initial stages, which is influenced by the fuel taking part in uncontrolled heat release phase. Once the auto-ignition of the fuel commences,

5 -811-

The Seventh International Conference on Modeling and Diagnostics for Advanced Engine Systems (COMODIA 2008), July 28-31, 2008, Hokkaido, Japan improved mixing and evaporation of ROME_H, which leads to complete burning.

fuel injection timing due to higher bulk modulus of compressibility, with the inline-fuel injection system which leads to a more rapid transferal of the pressure wave from fuel-pump end to the fuel-injector needle and the earlier needle lift causes an advanced (or early) injection (or combustion), which contributed towards large premixed combustion, which responsible for thermal ‘NO’ production. Another reason for large production of NO emission with the ROME is its oxygen content. The ROME is produced more ‘NO’ emission than PD fuel, especially at the higher engine loads as shown in figure 8. The oxygen (9.43%) content in this biodiesel may be the cause of this, as the more oxygen in biodiesel leads to better oxidation of the nitrogen available during combustion will raise the combustion bulk temperature responsible for thermal NO formation. The fuel spray properties may be altered due to differences in viscosity and surface tension. The spray properties affected may include droplet size, droplet momentum, degree of mixing, penetration, and evaporation. The change in any of these properties might be lead to different relative duration of premixed and diffusive combustion regimes. Since the two burning processes (i.e. premixed and diffused) have different emission formation characteristics, the change in spray characteristics due to preheating of the ROME is lead to reduction in NO formation. The reason is attributed to reduced intensity of premixed combustion regime (see figure 6) due to slightly retarded injection, better evaporation and well mixing of ROME_H, due to its lower viscosity at the temperature of 60 0C.

Exhaust Emissions Analysis: The exhaust emissions (NO, HC, CO, and Smoke) of the DI diesel engine is measured with the following instruments shown in the table 4 Table 4: Instruments used to Measure Emissions Emissions Instrument Model NO, HC, MRU Exhaust Gas Delta 1600 CO Analyzer, Germany L Smoke A V L Smoke Meter, 409 D (soot) Graz-Austria

650 600 550 500 450 400 350 300 250 200 150 100 50 0

Hydrocarbons: Figure 9 shows that, for PD and Biodiesel, the unburned hydrocarbons (HC) emissions are showing decreasing trend first and then increasing trend with power output. 200

PD

PD Hydrocarbons (ppm)

Nitric Oxide (ppm)

Nitric Oxide: Diesel engines produce negligible amount of NO2. Therefore, only NO is measured. The NO emission levels are shown in the figure 8 and the observations made are as follows: Results show that, for all the fuels, the increased engine load promoting NO emission. Since the formation of NO is very sensitive to temperature, these higher loads promote cylinder charge temperature, which is responsible for thermal (or Zeldovich) NO formation. The long chain biodiesel i.e. ROME is producing more ‘NO’ than PD fuel as shown in figure 8. The increase in NO emission might be an inherent characteristic of ROME’s MUFA (43%) and PUFA (38%) (see table: 1). Therefore, the fuel specific properties are responsible for NO formation. Fuel specific relationships were also observed between NO emission and peak heat release rates (see figure 6, 7 and 8). It is observed that, the higher the peak value of premixed combustion, the larger will be the NO formation.

ROME ROME_H

175

ROME

150

ROME_H

125 100 75 50 0

0

0.93

1.86

2.79

3.72

0.93

1.86 2.79 Power (kW)

3.72

Figure 9: Brake Power versus Unburned Hydrocarbons

Power (kW)

Figure 8: Brake Power versus NO for PD and BD Fuel

The reason for higher levels of HC at 0% load is attributed to the flame quenching and cooled layer of the charge near the cylinder wall during the cold start. However, the ROME_H is producing lower levels of

The production of more NO with ROME fueling is also attributable to an inadvertent advance of

6 -812-

The Seventh International Conference on Modeling and Diagnostics for Advanced Engine Systems (COMODIA 2008), July 28-31, 2008, Hokkaido, Japan HC emissions as compared to that of ROME, particularly at 0% load. The reason is attributed to improved spray pattern (due to its lower viscosity) and evaporation (due to temperature of 60 0C), which leads to efficient combustion. The HC emissions of the biodiesel are less than PD fuel. The reason for lower HC emissions is attributed to the higher cetane number (CN) of the biodiesel. The inherent presence of oxygen (9.43%) in the molecular structure of the ROME is also responsible for the lower HC emissions at all the loads.

effect of higher cetane number (58) and inherent oxygen (9.43%) present in the biodiesel, which improves the combustion. Therefore, it is concluded that, the increase of oxygen in the biodiesel fuel tends to reduce the smoke (soot) emission for all loads. The ‘C/H’ ratio for PD, and ROME is 6.9, and 6.61 respectively (see table: 2). Therefore, it is also concluded that the smoke (soot) emission increasing with the fuels ‘C/H’ ratio regardless of the molecular structure. That means, higher the carbon content in the fuel; the larger will be the smoke emission. At lower engine loads (0%and 25%) the high viscosity ROME showed a higher level of smoke than that of PD fuel. The reason is attributed to the poor quality of air-fuel mixing. A portion of the fuel-rich mixture may be fail to burn was emitted as smoke. The ROME_H is showed a lower level smoke than both PD and ROME, due to improved evaporation and mixing. However, at higher power outputs, the smoke emission is increasing for ROME_H. The reason is attributed to the late phase of combustion, particularly increase in diffusive combustion and complete burning of ROME_H during diffusive combustion mode, as compared to that of ROME (see figure 6) The PD fuel at higher loads showed a higher level of smoke than ROME and ROME_H. The reason is attributed to the presence of aromatics. Especially, the presence of branched and ring (multi-ring or poly cyclic) structures of the PD fuel can increase the smoke levels. And this increase in smoke emission was due to the higher boiling point and thermal stability of the aromatic hydrocarbons.

Carbon Monoxide: For both the fuels, the increasing trend of carbon monoxide (CO) emission levels are observed with load (see figure 10). These increasing trends of CO emissions are due to the increase in volumetric fuel consumption and knock with the engine load. The formation of CO emission mainly depends upon the physical and chemical properties of the fuel. It is observed that, the CO emission of ROME is more than that of PD fuel. The higher the peak pressure and rate of changes of pressure (see figure 3 and 5) the higher will be the knock levels. Therefore, the increase in CO emission for ROME is attributed to the possibility of knock and higher fuel consumption (due to its lower value of LCV), as compared to that of PD fuel. However, the CO emission levels are reduced for ROME_H and are on par with PD fuel, particularly at higher loads. The reason is attributed to its reduced viscosity, density and increase in evaporation rate. 0.1 PD ROME

0.08

Bosch Smoke Units

Carbon Monoxide (%)

0.09

ROME_H

0.07 0.06 0.05 0.04 0.03

4.5 4 3.5 3 2.5

PD

ROME

ROME_H

2 1.5 1 0.5 0 0

0.02 0

0.93

1.86

2.79

0.93

3.72

1.86

2.79

3.72

Power (kW)

Power (kW)

Figure 11: Brake Power versus Smoke (Soot)

Figure 10: Brake Power versus Carbon Monoxide

CONCLUSIONS This work confirms the influence of the higher bulk modulus of biodiesel on injection and combustion timing with the ‘in-line’ fuel injection systems. Highest peak pressures are observed with ROME. The peak pressures and the maximum rate of

Smoke: The figure 11 shows that, the smoke emission increases with engine load for all the above fuels. This increasing trend is attributed to the increase in volumetric fuel consumption with the power output. The biodiesel is emitting lower levels of smoke as compared to that of PD fuel under similar operating conditions. This is probably because of the combined

7 -813-

The Seventh International Conference on Modeling and Diagnostics for Advanced Engine Systems (COMODIA 2008), July 28-31, 2008, Hokkaido, Japan pressure rise are reduced with preheating of the biodiesel. Decrease in premixed combustion and increase in diffused combustion is observed with preheating. The reduction in peak value of premixed combustion is leads to the reduction of NO emission. The increase in NO emission with biodiesel is up to 12.9%. This is due to the combined effect of higher bulk modulus, and presence of unsaturated fatty acids (MUFA and PUFA) and oxygen. The reductions in hydrocarbons are up to 28% and reductions in smoke (carbon soot and particulate matter) are up to 40% with the ROME. These lower emissions levels are due to the combined effect of higher cetane number, oxygen content and lower C/H ratio Except smoke (soot), all the remaining emissions are reduced significantly with preheating of ROME. Improvement in diffused combustion is responsible for these increased smoke levels particularly at higher loads.

[9] Boukouvalas C J, Spiliotis N, Coustikos Ph, Tzouvaras N, Tassios DP. Fluid Phase Equilib 1994; 92:75. [10] Salunkhe, D.K., Chavan, J.K., Adsule, R.N., Kadam, S.S., 1991, World Oilseeds: Chemistry, Technology, and Utilization, Van Nostrand Reinhold, New Yorn. [11] http://www.suncarefuels.com/bdfoil.html [12] Van Gerpen, J.; Shanks, B.; Pruszko, R.; Clements, L.D.; knothe, G. Biodiesel analytical methods, August 2002-January 2004. National Renewable Energy Laboratory. NREL/SR-510-36240, July 2004, 95 p. [13] Lebedevas, S.; Vaicekauskas, A. “Improvement of the parameters of maintenance of medium speed diesels applying the motor methods”, Transport, Vol XVI, No. 6, 2004, p. 252-261. ISSN: 1648-4142. [14] Lebedevas, S. “NOx emisijos mazinimas dyzeliu ismetamosiose dujose taikant motorinius metodus”. Transportas (Transport Engineering), Vol XVI, No 4, 2001, p. 32-43. [15] Heinrich Prankl, Manfred Worgetter, Josef Rathbauer, “Technical Performance of Vegetable Oil Methyl esters with a High Iodine Number”. 4th Biomass Conference of the Americas. BLT Wieselburg (1999).

NOMENCLATURE PD: Petroleum Diesel BD: Biodiesel ROME: Rice bran Oil Methyl Ester ROME_H: Preheated ROME at 60 0C LCV: Lower Calorific Value

REFERENCES [1] Willard W. Pulkrabek, Engineering Fundamentals of the Internal Combustion Engine, ISBN -81-2032222-3 [2] http://www.ricebranoil.info/articles/popping.html [3] 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. [4] 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. [5] Jon Van Gerpen, “Biodiesel Production and Fuel Quality”, University of Idaho, Moscow, ID 83844. [6] D. Tapasvi, D. wiesenborn and C. Gustafson, “Process Model for Biodiesel Production from various Feedstocks”, Transactions of ASAE, ISSN 0001-2351, Vol. 48(6):2215-2221 [7] Aleks Kac, “The Two-Stage adaptation of Mike Pelly’s BiodieselRecipe”, (http://journeytoforever.org/biodiesel_aleks.html) [8] 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 -814-