Biodiesel from sunflower oil offers a potential as an alternative to petroleum-based diesel fuel and must be evaluated in terms of the resulting engine performance and exhaust emissions. Two diesel engines rated at 14.2 kW (small) and 60 kW (large) were operated on pure sunflower methyl ester (SFME) and its blends with a reference diesel (REFDIESEL). Results showed that less power and torque were delivered by both the small and large engines when ran on pure SFME than on REFDIESEL, while brake-specific fuel consumption (BSFC) was found to be higher in pure SFME. Blends of SFME with REFDIESEL (B5 and B20) showed negligible power loss and similar BSFC with the REFDIESEL. Higher concentrations of nitrogen oxides (
Biodiesel is an alternative fuel deemed to augment, if not to replace, petroleum diesel supply in the current world’s energy situation. It is a mixture of monoalkyl esters of long chain fatty acids (FAME) derived from a renewable lipid feedstock, such as vegetable oil or animal fat [
Biodiesel can be produced from the transesterification of any triglyceride feedstock, which includes oil-bearing crops, animal fats, and algal lipids [
Biodiesel production from sunflower oil has been widely investigated in various studies which include optimization of the transesterification process conditions, variation in catalysts, and blending with other oils prior to biodiesel production [
Aside from engine testing, emissions associated with the use of biodiesel also need to be evaluated to assess its cleanliness as a fuel. The Environmental Protection Agency (EPA) reported that nonroad diesel engines have a substantial role in contributing to the nation’s air pollution, and therefore stricter emission standards were imposed with regards to the amounts of particulate matter, nitrogen oxides, and sulfur oxides [
Thus, the application of biodiesel produced from sunflower oil as an engine fuel is investigated in this study and compared with those of soybean oil biodiesel and a reference petroleum diesel. The main objective is to evaluate the performance of sunflower methyl ester as an engine fuel in terms of engine performance and emission characterization. In particular, this study aims to (a) assess fuel properties of the sunflower methyl ester in accordance with ASTM standards; (b) determine the effect of blending percentage of biodiesel on the characteristic engine performance (i.e., net brake power, torque, and specific consumption); (c) determine the relationship between pollutant concentrations (i.e.,
Sunflower oil biodiesel (SFME) was prepared from previously extracted and refined oils at the Bio-Energy Testing and Analysis (BETA) Laboratory at Texas A&M University, College Station, TX. The following conventional biodiesel reaction conditions were used: reaction time, 1 h; weight of catalyst, 0.4% wt. of initial oil weight; vol. of methanol, 15% vol. of oil; reaction temperature: 50°C. The biodiesel obtained was then blended with a reference diesel (REFDIESEL-ULSD standard no. 2 reference fuel). The test fuels were analyzed to determine if they meet ASTM 6751-07 standard. Fuels and fuel blends are as follows: 5% SFME-95% REFDIESEL-B5 SFME, 20% SFME-80% REFDIESEL-B20 SFME, 100% SFME-0% REFDIESEL-B100 SFME.
Soybean oil biodiesel (SME) and the reference diesel were purchased commercially.
ASTM characterization of the biodiesel was done to ensure that the test fuel used in the study conforms to the ASTM D6751-08 standard (ASTM, 2008). Some of the referenced procedures in the ASTM 6751 standard were conducted in the BETA lab. Such procedures were cloud and pour point (ASTM D2500), flash point (ASTM D93), water and sediment (ASTM D2709), kinematic viscosity (ASTM D445), acid number (ASTM D664), and gross heating value (ASTM D4809).
Engine performance and exhaust emissions testing were conducted at the BETA Lab engine testing facility. Instrumentation needed to measure some of the EPA regulated emissions, such as CO, CO2,
The BETA lab uses two test engines with their own respective test beds and dynamometer set-ups. One of the test engines was a 3-cylinder Yanmar 3009D diesel engine rated at 14.2 kW (Figure
General specifications for Yanmar 3009D and JD4045DF150 diesel engines.
Specification | Yanmar 3009D | JD 4045DF150 |
---|---|---|
Rated power | 14.2 kW (19 hp) at 3000 rpm | 60 kW (80 hp) at 2700 rpm |
Number of cylinders | 3 | 4 |
Bore | 72 mm | 106 mm |
Stroke | 72 mm | 127 mm |
Displacement | 0.879 L | 4.5 L |
Compression ratio | 22.6 : 1 | 17.6 : 1 |
Combustion system | Indirect injection | Direct injection |
Aspiration | Natural | Natural |
The dynamometer test system showing the (a) 14.2 kW-Yanmar 3009D diesel engine and (b) the dynamometer.
The large test engine used in the study, shown in Figure
Properties of test fuels and the reference diesel according to ASTM standards.
Property | Method | Specifications | Reference diesel | Sunflower ME | Soybean ME |
---|---|---|---|---|---|
Flash point, °C | D93 | 130 min. | 128 | 192 | 199 |
Water and sediment, %vol | D2709 | 0.050 max. | <0.01 | <0.01 | <0.01 |
Kinematic viscosity, 40°C, mm2/s | D445 | 1.9–6.0 | 2.3 | 6.3 | 4.7 |
Sulfur, ppm | D5453 | 15 max. | Unknown | Unknown | 4 |
Cetane number | D613 | 47 min. | Unknown | Unknown | 55 |
Cloud point, °C | D2500 | Report | −35 | 2 | −6 |
Carbon residue, %mass | D4530 | 0.050 max. | Unknown | Unknown | 0.01 |
Acid number, mg KOH/g sample | D664 | 0.50 max. | 0.04 | Unknown | 0.19 |
Distillation temperature, °C | D1160 | 360 max. | Unknown | Unknown | 329 |
Oxidation stability, hours | EN14112 | 3 min. | Unknown | Unknown | 7.2 |
Gross heating value, MJ/kg | D4809 | Report | 42.7 | 38.2 | 38.8 |
JD 4045DF150 diesel engine used for performance and emissions testing.
Figure
Schematics of the data acquisition system for the Yanmar 3009D and JD 4045DF150 diesel engines.
National Instruments (NI) data acquisition equipment (DAQ) was installed in different parts of the test engines and the test cell. A fiber optic cable connects the remote computer to the NI PCI-7831R FPGA module. Thermocouples and pressure transducers were connected to the SCXI 1320 and SCXI 1326 signal conditioning units. Torque and engine speed data are collected using a NI Labview program developed for this research. Exhaust emissions such as CO,
The emissions analyzer has a capability of measuring 0 to 3500 ppm
Engine power tests are conducted in accordance with SAE Standard Engine Power Test Code for diesel engines (SAE J1349 Revised MAR2008). Baseline engine performance and emissions tests are performed using ULSD reference diesel fuel. Engine performance data for ULSD reference diesel were corrected to the standard atmospheric conditions using the compression ignition engine correction formula according to SAE J 1349-MARCH2008.
Variables such as air and relative humidity are carefully monitored. Fuel temperature is controlled as outlined in the test procedure. Tests were conducted in a randomized complete block design (RCBD) to prove that the fuel sequence is not significant to the results of the study. Response variables were the following: net brake power (kW), torque (N-m), fuel consumption (L/h),
The BETA lab is equipped with a NI Labview program that can perform remote-based switching of fuel source. This provides changing of test fuels without turning off the engine. At each fuel change, the fuel filter was replaced and then the engine was warmed at idle speed on the new fuel for 15 minutes to purge remaining previous test fuel from the engine’s fuel system. Then, the engine was operated at full throttle and prepared for the next performance testing. Also, a new set of sintered filters for the exhaust emissions analyzer was installed prior to the next emissions testing.
The important sources of uncertainty in this study are (1) supply of consistent quality of fuel, (2) proper control over relevant engine parameters (e.g., speed and load), and (3) proper use and calibration of the measurement instruments. To minimize the first source of uncertainty, test fuels were processed in such a way that it will match up ASTM 6751 standard. Fresh batch of biodiesel was used to ensure consistency of the fuel quality in the experiment. The uncertainty associated with the second source was minimized by depending on the proper control and the use of engine instrumentation and controller equipment. Parameters, such as engine speed, fuel flow rate, and load accuracy, were matched to within ±5 RPM, ±1% of the reading, and ±0.05% of the rated output, respectively. Finally, the uncertainty associated with the third source was minimized by calibrating emissions equipment, each day prior to start of testing, and all other instruments (pressure transducers, thermocouples, flow rate meters, etc.) on routine basis.
In order to understand the effect of the biodiesel on engine combustion efficiency, the brake specific fuel consumptions (BSFC) for the test fuels and each fuel blend were measured at peak torque condition. This condition was chosen since it is the point of minimum air/fuel ratio and maximum smoke [
Table
The performances of the engines at full load (the fuel pump is at the maximum delivery setting) using test fuels (SFME, SME, and PME-REFDIESEL blends) were determined in accordance to SAE J1349 Power test code procedures. Baseline engine performance and emissions tests were performed using standard no. 2 ULSD fuel (REFDIESEL). Corrected values of the net brake power and brake-specific fuel consumption for ULSD, as described earlier, were also presented in the following sections.
Net brake power of the Yanmar engine at various SFME-REFDIESEL fuel blends and engine speeds.
Comparison with different fuel blends shows that the net brake power decreased with an increase in the percentage of SFME in the blend. However, statistical analysis showed no significant differences among the REFDIESEL, B5 and B20, fuel blends. The corrected net brake power of REFDIESEL was at 13.95 kW, which is 4.5% higher than the peak net brake power for B100 SFME with 13.3 kW. A study by Kaplan et al. in 2006 [
The performance of SFME was also compared to that of soybean biodiesel (SME), and the net brake power at different engine speeds is shown in Figure
Net brake power of the Yanmar engine using SFME, SME and REFDIESEL at varying engine speeds.
Many studies agree that the use of biodiesel will lead to the reduced engine power and that using fuel blends with small percentages of biodiesel will result in unnoticeable power loss. The decrease in engine power can be attributed to the lower heating value of SFME as compared to the reference diesel. High viscosity of the biodiesel can also have certain effects on the engine power [
Net brake power of the John Deere engine using SFME, SME, and REFDIESEL at varying engine speeds.
Engine torque of the Yanmar engine at various fuel blends and engine speeds.
The peak torque values for different SFME blends were lower than the reference diesel by as much as 2%. Among the fuel blends, B20 SFME has the highest peak torque (46.5 N-m), followed by B100 then B5. The reference diesel has a peak torque of 47.0 N-m at a speed of 2700 rpm. The slight decrease in torque can as well be attributed to the lower heating value of SFME. Nevertheless, it can be seen from Figure
Engine torque of the John Deere engine using SFME, SME, and REFDIESEL at varying engine speeds.
Brake specific fuel consumption (BSFC) of the Yanmar engine at various fuel blends and engine speeds.
At peak torque conditions, the BSFC was found to increase when using pure SFME but has no significant difference among the REFDIESEL, B5 and B20, fuel blends. An increase in BSFC was also observed by Moreno et al. [
The BSFC for SFME was also compared with those for SME and REFDIESEL as shown in Figure
BSFC of the Yanmar engine using SFME, SME, and REFDIESEL at varying engine speeds.
BSFC of the John Deere engine using SFME, SME, and REFDIESEL at varying engine speeds.
To summarize, SFME delivered less power and torque in reference to pure diesel fuel when used in both small and large engines. They were also found to decrease with increasing percentage of SFME in the fuel blends. The use of SME resulted in more power as compared with SFME. Power is a function of the engine geometry, speed, air/fuel ratio, efficiencies, and fuel properties. Assuming that mechanical losses are similar and since there were no modifications made in the injection rates or duration for an individual test fuel, power loss may be attributed to the variation in the fuel properties such as heating values and densities between fuels.
Moreover, the rise in mass flow for all biodiesel fuels as observed from both engines can be attributed to the differences in the heating values of the test fuels. The biodiesel fuels have approximately 10% lower heating values than the reference diesel. The heating value affects the torque being produced, and in order to match that torque with REFDIESEL, pure biodiesel and its blends with REFDIESEL will have to put more energy in the engine, resulting in higher fuel consumption. Also, as far as engine performance is concerned, it was determined based on the statistical analyses performed on BSFC at peak torque conditions for both engines that the BSFC of 100% SME and SFME were statistically the same. The BSFC of both fuels, however, are higher (5–14%) than the REFDIESEL.
Since the composition of the fuel affects the emissions of an engine, emissions from biodiesel fuel are also different as compared to those of petroleum diesel. Due to its higher oxygen content (
Some of the EPA regulated emissions determined in this research were CO, CO2,
The trends observed concerning
Various exhaust emission concentrations at different SFME fuel blends for the Yanmar diesel engine.
Figure
Finally, the emission of carbon monoxide in the outlet gases decreased as the content of SFME was increased. It reached a minimum at 20% SFME then gradually increased as the percent of SFME reached 100%. The CO emission is much lower when using pure SFME than when using the reference diesel. Several studies also reported lower CO emission for SFME as compared with diesel fuel [
The emissions of SFME were also compared with those when using SME as shown in Figure
Various emission concentrations of the Yanmar engine using SFME, SME, and REFDIESEL at varying engine speeds.
The emissions were also determined for the large John-Deere engine. Figure
Carbon monoxide, carbon dioxide, and total hydrocarbon concentrations for biodiesel fuels were relatively higher than those for REFDIESEL (Figure
Various exhaust emissions of the John Deere engine using SFME, SME, and REFDIESEL at varying engine speeds.
The engine performance and exhaust emissions were evaluated for small and large engines operated on pure SFME and its blends with a reference diesel. SME was also tested for comparison purposes. Results showed that less power and torque were delivered by both the small and large engines when ran on pure SFME and SME, while BSFC was found to be higher as compared to the reference diesel. Blends of SFME with REFDIESEL (B5 and B20) showed negligible power loss and similar BSFC with the REFDIESEL. Meanwhile, analyses of the exhaust emissions of the engines when ran on different fuel blends and on pure SFME and SME showed higher
The authors of the paper do not have a direct financial relation with the commercial entities mentioned here that might lead to a conflict of interests for any of the authors.