6340(Print), ISSN (Online) TECHNOLOGY Volume 3, Issue (IJMET) 2, May-August (2012), IAEME

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1 INTERNATIONAL International Journal of JOURNAL Mechanical Engineering OF MECHANICAL and Technology ENGINEERING (IJMET), ISSN 0976 AND 6340(Print), ISSN (Online) TECHNOLOGY Volume 3, Issue (IJMET) 2, May-August (2012), IAEME ISSN (Print) ISSN (Online) Volume 3, Issue 2, May-August (2012), pp IAEME: Journal Impact Factor (2012): (Calculated by GISI) IJMET I A E M E LARD BIODIESEL ENGINE PERFORMANCE AND EMISSIONS CHARACTERISTICS WITH EGR METHOD S.H. Choi 1), Y.T. Oh 2)* and J. Azjargal 3) 1) Department of Automation Mechanical Engineering, Vision University of Jeonju, Cheonjam-ro, Wansan-gu, Jeonju, , Republic of Korea 2) Faculty of Mechanical Engineering, Chonbuk National University, Jeonju , Korea 3) Department of Mechanical Engineering, Graduate School of Chonbuk National University, Jeonju , Korea *Corresponding author: ohyt@jbnu.ac.kr ABSTRACT The aim of this study mainly was to quantify the cooled exhaust gas recirculation (EGR) effects on direct injection diesel engine performance and exhaust emissions when using biodiesel (BD) from lard at various engine operations. The lower calorific value of lard BD results in increased fuel consumption but the engine thermal efficiency is not affected significantly. Engine torque and power were reduced slightly at high EGR rate, while the brake specific fuel consumption increased 2.75 % with lard BD. It was observed that the NOx emission evidently decreased up to 58 % by using lard BD with EGR rate of 30 %. And this experimental work results showed that, simultaneous reduction of NOx and smoke emission was achieved with applying lard BD 10 with optimum EGR ratio between 5 to 10 %. Also, smoke and CO emissions of lard BD were lower than commercial diesel at all EGR rates. Keywords: Alternative fuel, Animal fat, Combustion, Transesterification, Exhaust gas 397

2 1. INTRODUCTION BD as an alternative engine fuel needs to be produced from less expensive fats, including inedible lard, pork lard and other animal fats. These raw materials can be suitable for BD production. Their high cetane number and heating values are close to those of the diesel fuel and their oxygen content provides additional advantages. The waste frying oils are scarce but waste animal fats are more abundant [1]. Animal fats are highly viscous and mostly in solid form at ambient temperature because of their high content of saturated fatty acids. However, high quality BD production from lard is possible by using synthesis with high solvent additive [2]. It has been concluded by many studies that BD fueled engine can reduce the emissions of CO, HC, SO 2, PAH, and smoke but NOx to increase in the exhaust compared with diesel fuel. Research work results showed that EGR is one of the most effective method used in modern engines for reducing NOx emissions. EGR involves replacement of oxygen and nitrogen of fresh air entering in the combustion chamber with the carbon dioxide and water vapor from the engine exhaust. The recirculation of exhaust gases into the engine intake air increases the specific heat capacity of the mixture and reduces the oxygen concentration of the intake mixture. These two factors combined lead to significant reduction in NOx emissions [3]. Difficult starting, rough idling, reduced performance and fuel economy resulted by using EGR system. Also excessive EGR rate in poorly set up applications can cause misfires and partial burns. But modern engine systems utilizing electronic engine control computers, multiple control inputs, and servodriven EGR valves typically improve performance/ efficiency with no impact on drivability [4-6]. The experimental study of animal fats as alternative fuels in diesel engine with EGR has not been developed extensively. Therefore, this experimental work has good advantages to investigate lard BD combustion characteristics in a diesel engine equipped with EGR apparatus. Agarwal et al. [3] tested a vegetable oil BD in two-cylinder engine equipped with EGR and found that the 15 % EGR and 20 % BD blend was the optimum combination. Choi and Oh [4] observed simultaneous reduction of smoke and NOx emission could achieve by the combination of oxygenated blended fuels and cooled EGR method in both DI and IDI diesel engines. Qi et al. [5] concluded that the use of BD fuel could decrease the smoke and NOx from six-cylinder engine equipped with EGR under certain engine conditions when compared to diesel. Pradeep et al. [6] reported that optimal EGR level was 15 % based on adequate reduction in NOx emissions, minimum possible smoke, CO, HC emissions and reasonable brake thermal efficiency. Tsolakis et al. [7] investigated a single-cylinder direct injection diesel engine equipped with cooled EGR and they concluded that the use of EGR was more effective in the case of BD blends combustion compared to diesel fuel combustion. And NOx emissions were reduced at levels similar to those of diesel fuel with the use of similar volumetric percentages of EGR while the smoke was kept low. The objective of this experimental study was to investigate the optimal conditions of cooled EGR system when using lard BD as a renewable fuel for engine harmful emissions reduction, especially NOx. And EGR effects on engine performances as power, torque and fuel economy for all various engine operating conditions were analyzed in this paper. 398

3 2. MATERIALS AND EXPERIMENTAL PROCEDURE 2.1 Biodiesel synthesis and properties of lard BD Lard BD was prepared by transesterification with methanol in the presence of KOH as catalyst to synthesize BD fuel. Commercial purified lard was provided by Samyang (South Korea) from a local market and used without any further purification. Methanol (99.5 %) and potassium hydroxide powder (95.0 %) used for transesterification were purchased from Samchun pure chemical Co.,Ltd. (South Korea). The suitable condition for high quality BD production from lard was found in previous research study [2]. A sample of 300 ml of lard was placed in a flat-bottom flask equipped with a magnetic stirrer-heater. The lard was heated to 57 C slowly until melted and blended with 200 ml solvent. In another beaker, 350 g of methanol (the methanol/lard mole ratio was selected at 10:1) was mixed with 10.5 g of potassium hydroxide, until all of the KOH was dissolved in methanol. This mixture was then added to the melted lard, stirred rigorously, and further heated to 60 C, close to the boiling point of methanol, for 90 min. It was observed that the FAME concentration was approximately constant around this time. The mixture was then transferred to a separator funnel, and glycerol was allowed to separate for a minimum of 3 h. After draining off the glycerol, FAME was washed twice with 1:1 volume of water for 1.5 h to remove excess methanol. Finally, lard BD was purified by distilling and dried at room temperature. All properties of lard BD analyzed by Korean Institute of Petroleum Management and predicted cetane number [8] were determined (Table 1). The properties were compared with ASTM D and EN standards and the final products fulfilled all of the requirements of these standards. The lard BD s most important parameters like viscosity and density met the specifications required by ASTM and EN standards. Lard BD is nonflammable and, in contrast to commercial diesel, is non-explosive, with a higher flash point of 130 C and it makes the storage safer. Lard BD has higher cetane number than diesel fuel and this can help the engine start more quickly and run more quietly. The presence of monounsaturated compounds gave the lard BD a higher cetane number. Animal fats are highly saturated, which means that the fat solidifies at a relatively high temperature. Therefore, BD made from animal fat has a high pour point. But this study result of lard BD s pour point and cold filter plug points meets the limits by ASTM standard. The primary reason for these good agreements is probably that high blending rate of solvent during synthesis enhanced complete conversion of lard s long chain molecules. The calorific value of lard BD is about 38.8 MJ/kg, being 9.13 % lower than the one of commercial diesel. In this experiment, commercial diesel fuel was blended with 5 and 10 % volume mixed ratio of lard BD (BD 5 and BD 10, respectively). Fuel viscosity is important because it affects the atomization of the fuel being injected into the engine combustion chamber. The mixture properties of kinematic viscosity and density of lard BD are presented in Table 2. Masses and volumes were determined and the electronic balance CAS-CUW- 8200S/Philippines as used to measure the density of different fuel mixtures. And kinematic viscosities were measured by using the Brookfield Viscometer LVT /USA. 399

4 Table 1 Properties of lard BD and commercial diesel fuel Properties Lard BD ASTM D EN Density, (kg/m 3 ) Viscosity, (mm 2 /s) Cetane number 57.8 >47 >51 Flash point, ( C) 130 >130 >120 Pour point, ( C) to 10 - Cold filter plug point, ( C) to 12 - Calorific value (MJ/kg) Carbon residue (wt.%) 0.03 <0.05 <0.3 Sulfur content (mg/kg) 1.00 <0.05 <10 Sulfated ash (wt.%) <0.02 <0.02 Total glycerin (wt.%) <0.24 <0.25 Methanol content (wt.%) <0.2 Table 2 Viscosity and density properties of experimental fuels Fuels Density, [kg/m 3 ] Viscosity, [mm 2 /s] diesel fuel BD BD EXPERIMENTAL APPARATUS AND METHODS The engine used in this experiment was a single cylinder, water-cooled, 4 stroke, direct injection diesel engine. The engine load and rotational speed was adjusted by using a dynamometer. The basic specifications of the engine are shown in Table 3. A schematic 400

5 diagram of the engine setup is shown in Fig. 1. In the experiments, first the engine was started with diesel fuel and when the engine reached the operating temperature, and then BD fuel was used. Effective engine power, torque and brake specific fuel consumption (BSFC) were calculated. The engine was operated with 80±2 C cooling water under all operating conditions. The engine was tested with loads ranging from 0 % and 100 % at 25 % intervals. A specific case of 90 % load was also investigated. Also the engine was operated at various engine speeds (range of rpm at 400 rpm intervals), and was loaded with a hydraulic dynamometer. Brake mean effective pressure (BMEP) was chosen from 0.2 to 0.6 in 0.1 steps. Greenline MK2/Italy gas analyzer was used to measure exhaust emissions. Before the measurements, the gas analyzer instrument was calibrated and its probe was inserted into the exit of exhaust pipe, which is 300 mm away from the exhaust manifold. In the tests, CO 2 (%), O 2 (%), CO (ppm) and NOx (ppm) were measured by these instruments. The Hesbon-HBN1500/Korea model smoke meter was used to measure smoke emissions concentrations. The concentration of smoke adsorbed on the filter paper was measured under the same measurement conditions, and then the average of every three values was used for the analysis. The laminar flow element provides for a certain pressure drop across itself for a certain volumetric flow rate of air. This pressure drop was measured using an inclined digital micro manometer DP-100A/Japan. EGR ratio is a term indicating the ratio of fresh air reduced by the regeneration process of EGR [4] and is expressed as the formula (1) below, where V o is intake air volume (m 3 /h) when no EGR was performed and V a (m 3 /h) is that when EGR was performed. (1) It was necessary to connect the exhaust manifold with the air intake manifold, with a filter, a heat exchanger and an EGR valve at this connection. The filter is used for particulate reduction and supply of clean gas for EGR. The heat exchanger is used as an exhaust cooler for cooling exhaust gas by water flow. An EGR valve was installed in this connection that enabled manual control of the flow rate of EGR to the intake manifold to attain various EGR ratios. Sufficient distance for thorough mixing of fresh air and exhaust gases were ensured. In this study EGR rate increased gradually by an EGR valve from 5 % to the 30 % to optimize NOx emissions reduction. 401

6 Fig. 1 Schematic diagram of experimental apparatus. Table 3. Basic technical specifications of the test engine. Model Items Specification ND130 Numbers of cylinder 1 Combustion chamber type Toroidal type Bore x Stroke 95 x 95 Displacement, [cc] 673 Compression ratio 18 Injection timing, [ C] BTDC 23 Coolant temperature, [ C] 80±2 402

7 3. RESULTS AND DISCUSSION 3.1 Lard BD engine performance with EGR apparatus A cooled EGR method was applied in this experiment for increasing volumetric efficiency. Many researchers have used EGR after cooling to room temperature. This method even though effective, is expensive and difficult to implement. Exhaust gases being at high temperature, a properly designed water cooler is necessary. Practical difficulties faced in a cooled EGR system viz. corrosion of cooler, cooling capacity at higher load, extra weight. While EGR is effective in reducing NOx, it also has adverse effects on the engine efficiency and may cause pollution of lubricating oil and corrosion of inlet manifold and moving parts, as exhaust gas contains a lot of particulate matter [9]. The application of EGR can also adversely affect to the engine durability [3]. Fig. 2 shows the power, torque of the diesel engine with EGR when applying the experimental blended BD fuels at 90 % load and engine speed of 2000 rpm. A little power reduction occurs with increase of BD concentration in the blends with EGR. As shown in this Figure, there was a highest power reduction of 3.95 % when at high EGR rates of 30 % with lard BD 10 in comparison with commercial diesel due to reduced heat content of BD. Also from this Figure it s seen that power reduction percent increased as EGR rates grow. Power reduction rate was slowly for lard BD blends than that of conventional diesel, even at higher EGR rates. The engine torque in the case of the lard BD blend is slightly lower than diesel at all engine speeds. The experimental results of both lard BD and commercial diesel fuels indicate that the engine torque was reduced slightly as increase EGR rates. The engine torque with lard BD is lower than that with diesel fuel by 3.23 %, 3.77 % for lard BD 5 and 10, respectively at 30 % EGR rate. It is well known that the heating value of the fuel affects the performance of an engine. Although the heating value of the lard BD is 9.14 % less than that of the diesel fuel, lard BD addition did not cause any large reduction rate in the torque and power of the engine. Power [kw] Engine load 90%, 2000 rpm diesel fuel BD 5 BD Torque [Nm] EGR rate [%] Fig. 2. Engine power and torque versus various EGR rates. 403

8 BTE [%] Engine load 90%, 2000 rpm EGR 0% EGR 5% EGR 10% EGR 15% EGR 20% EGR 30% BSFC [g/ps h] diesel fuel BD 5 BD 10 Fig. 3. Comparison of BTE and BSFC with various EGR rates and lard BD fuel blends Brake Thermal Efficiency (BTE) of an engine is the efficiency in which the chemical energy of a fuel is turned into useful work. The BTE of an engine depends on number of factors but the most meaningful property is heating value and specific gravity. And BTE indicates the ability of the combustion system to accept the experimental fuel and provides comparable means of assessing how efficiently the energy in the fuel was converted to mechanical output. Fig. 3 illustrates the variation of the EGR ration the BTE and BSFC with lard BD and diesel fuel at 90 % load and engine speed of 2000 rpm. The engine BTE was not affected significantly from the combustion of BD fuel blends with EGR. At high EGR, the engine BTE reduction for diesel fuel was 2.66 % but when engine operated on BD, the maximum reduction for BTE was only 1.6 % for lard BD 10. This might be attributed because of unburned HC s would possibly re-burn in the mixture again with EGR. Also this slight reduction of BTE with lard BD mixtures was attributed to poor spray characteristics, poor air fuel mixing, higher viscosity, higher volatility and lower calorific value. Pradeep et al. [6] concluded that this drop of BTE is possibly due to predominant dilution effect of EGR leaving more exhaust gases in combustion chamber. BSFC is one of the important parameters of an engine and is defined as the consumption per unit power in a unit of time. The BSFC of diesel engine depends on the relationship among fuel density, viscosity and lower heating value. BSFC of lard BD blends were slightly higher for all levels of EGR compared to corresponding diesel fuel values. This is presumably due to lower calorific value, higher boiling point and viscosity of lard BD. In this study, BSFC increased up to 3.28 % for diesel whereas it was 2.32 %, 2.75 % for lard BD 5 and BD 10, respectively at high EGR rate of 30 %. Increasing the EGR rate above 15 %, the combustion of mixture deteriorates. Therefore, more BD and its blends are 404

9 needed to produce the same amount of energy due to its lower heating value in comparison with diesel fuel. 3.2 Engine exhaust gas analysis with various EGR rates The diesel engine exhaust gases mainly consist of inert carbon dioxide, nitrogen and possess high specific heat. When recirculated to engine inlet, it can reduce oxygen concentration and act as a heat sink. This process reduces peak combustion temperature, which results in reduced NOx. Chemical effect of EGR is to participate of carbon dioxide in the combustion process. Thermal effect refers to the increase in inlet charge thermal capacity due to the recirculation of exhaust gas. Fig. 4 shows CO curve versus EGR rates with various experimental BD fuel blends. It is important to measure the quantity of CO emissions in the exhaust gases when the diesel engine was operated with BD, because it is an indicator of the completeness of the combustion. Generally, CO emission is affected by air-fuel equivalence ratio, fuel type, combustion chamber design, atomization rate, SOI timing, engine load and speed. The most important thing among these parameters is the air-fuel equivalence ratio [10]. For the BD fuel blends, the CO emissions were less than for the diesel fuel at all EGR application rates. CO emission was rapidly increased from EGR rate of 15 % and very high CO values for all experimental fuels might be due to the oxygen deficient operation. Also the combustion quality worsens with the increase of EGR rate. For lard BD, the excess oxygen content is believed to have partially compensated for the oxygen deficient operation under EGR. CO emission reduction rate was higher between 5 to 15 % EGR rate conditions and this rate decreased gradually with increasing EGR rate due to incomplete combustion, higher viscosity of lard BD fuel. So the presence of atomic bound oxygen in the lard BD fuel satisfies positive chemical control over CO formation. CO 2 emission is produced by complete combustion of fuel. CO 2 is a most important component in the global warming. Many researchers claimed that all of the carbon released by combustion of the BD has been fixed by the plant through the process of photosynthesis ratio. Fig. 4 also shows the effect of lard BD percentage and EGR rates effects on CO 2 emissions. While the test engine was running with the lard BD, CO 2 emission was lower until 17 % EGR rate but further increase of EGR rate, BD s CO 2 emission grows very rapidly and gets higher than that of diesel. While there was an approximately linear relationship between CO 2 formation of the commercial diesel and EGR rates, but same relationship for lard BD was not appeared. The lard BD revealed an increase in CO 2 emissions because of its oxygen content which affected the mixture when volumetric efficiency decreased at the high EGR rates. Also BSFC of BD improved at the high EGR rates due to the lower heating value, thus lard BD emitted more CO 2 emissions compared to that of diesel fuel. 405

10 CO [ppm] diesel fuel BD 5 BD 10 Engine load 90%, 2000 rpm EGR rate [%] Fig. 4. Comparison of experimental fuels CO and CO 2 emission at various EGR rates In diesel combustion the local NOx formation in the spray is related to the local oxygen atom concentration. Animal fat BD usage generally results in higher NOx emissions despite its high cetane number in comparison commercial diesel fuel. It is shown that EGR rates produced a corresponding decrease in NOx emissions. This is caused mainly by exhaust gas dilution of fresh air which causes a decrease of oxygen concentration of in cylinder combustible mixture and a decrease of in-cylinder temperature. Fig. 5 shows the lard BD 10 fuel s NOx and smoke concentration versus engine BMEP at various EGR rates and engine speeds. NOx emissions were higher for lard BD without EGR. But with the increase of the EGR rate by 5 %, the NOx emission is decreased by about 15 %. For lard BD operated engine large EGR rates (15-30 %) can be used for high reduction efficiency of NOx (50-75 %) without obvious increase of BSFC (less than 5 %) CO 2 [%] 10 Smoke [%] rpm diesel fuel, W/O EGR BD 10, EGR 5% BD 10, EGR 10% BD 10, EGR 15% BD 10, EGR 20% BD 10, EGR 30% BD 10, W/O EGR diesel fuel, EGR 30% NOx [ppm] Smoke [%] rpm NOx [ppm] BMEP [MPa] 0 Fig. 5. Comparison of NOx and smoke emission of experimental fuels with and without EGR 406

11 Smoke particles formed from the fuel deposited on the walls. Also smoke emission is defined as the presence of carbon particles in the exhaust as a result of incomplete combustion. Generally, in diesel engine the fuel is richer than stoichiometric air-fuel ratio; the part of fuel is incompletely burned due to lack of air so the more smoke is generated. Fig. 5 also presents effect of lard BD s smoke emission, which was conducted with various EGR rates. By applying EGR rates up to 10 % the smoke emission of lard BD 10 was lower than that of diesel fuel basic data level as seen from this Figure. Thus, it is very important that when applying lard BD 10 fuel and optimum EGR ratio until 10 % would be simultaneous reduction of NOx and smoke emission. If BD fuel was supplied to the diesel engine, the oxygen component in blended fuel would be an oxidized hydrocarbon component, and it was capable of reducing smoke density during the combustion period. The smoke emission tends to increase as EGR rate increase. This was considered to be due to lack of oxygen in inlet air. The smoke emission increase amount of commercial diesel fueled engine was 38.8 % whereas it was lower than that of diesel as 33.1 %, 28.3 % for lard BD 5 and BD 10, respectively at high speed condition. The result of low smoke level with lard BD in comparison diesel is explained by the presence of fixed carbon in the animal fat with excess oxygen concentration and higher cetane number than commercial diesel fuel. As EGR rates increases, diesel engines tend to generate more smoke because of reduced oxygen. Therefore, EGR, although effective to reduce NOx, further increases the smoke and PM emissions. Also EGR is typically not employed at high loads because it would increase smoke rapidly. Fig. 6 shows the smoke reduction and NOx increase rate compared to commercial diesel fuel at various EGR rates and lard BD blended fuels. At low EGR rate until 15 %, the NOx decrease rate was always higher than smoke increase rate and further increase of EGR, that NOx reduction rate was similar as smoke increase rate. At 2000 rpm, in case of 30 % EGR rate application, the smoke increase rates were 1.5, 1.45 and 1.4 but NOx decrease rates were 1.62, 1.75 and 1.58 for lard BD 10, 5 and diesel, respectively. Thus, BD fuel operated engine has lower smoke increase and much higher NOx decrease than commercial diesel fueled engine with EGR. This effect could be explained by the fact that oxygen contents in the lard BD likely improved complete combustion [4]. Therefore, lard BD is a more efficiency fuel with application of cooled EGR method for high speed diesel engine than commercial diesel fuel. Smoke increase rate diesel fuel BD 5 BD 10 NOx decrease rate Engine load 90%, 2000 rpm EGR rate [%] Fig. 6. Comparison of smoke increase rate and NOx decrease rate in comparison with diesel fuel on various EGR rates 407

12 4. CONCLUSION This experimental study was investigated the DI-diesel engine performance and exhaust emissions by using animal fat BD (lard BD 5 and 10) at different EGR rates of 5-30 %. The significant points emerged from the current study are: 1. The maximum BSFC increase rate was 2.75 % and torque, power were decreased only by 3.77 and 3.95 %, respectively with addition of lard BD 10 and EGR rate of 30 %. This performance reduction causes by lower calorific value of lard BD. The engine BTE was not affected significantly from the combustion of BD fuel blends with EGR. At high EGR, the engine BTE reduction of diesel fuel was 2.66 % but for lard BD 10 this reduction was only 1.6 %. 2. CO emissions of lard BD were lower than diesel at all EGR rates and maximum reduction rate was 6.9 % at 15 % EGR rate. While the test engine was running with the lard BD, CO 2 emission percent was lower until 17 % EGR rate, but further increase of EGR rate leads to growing lard BD s CO 2 emission rapidly and gets higher than that of diesel. The lard BD s NOx emission significantly decreased with cooled EGR. At high EGR rates of 30 %, the lard BD 10 fuel operated engine NOx reduced up to 75 % than that of diesel basic data. As EGR rates increases, diesel engines tend to generate more smoke but the highest smoke emission increase amount was 38.8 % for diesel whereas it was 33.1 %, 28.3 % for lard BD 5 and 10, respectively. Lard BD fuel operated engine has lower smoke increase rate and much higher NOx decrease rate with EGR. Simultaneous reduction of NOx and smoke emission was possible with application of optimum EGR ratio of 10 % and applying lard BD 10 (or lard BD 5 with 5 % EGR rate). REFERENCES [1] J.M. Dias, M.C.M. Alvim-Ferraz, M.F. Almeida, Production of biodiesel from acid waste lard, Bioresource Technology, vol. 100, pp , 2009 [2] J. Azjargal, Y.T. Oh, S.H. Choi, High quality biodiesel production from pork lard by high solvent additive, ScienceAsia, vol. 38, pp , 2012 [3] D. Agarwal, S.Sinha, and A.K. Agarwal, Experimental investigation of control of NOx emissions in biodiesel-fueled compression ignition engine, Renewable Energy, vol. 31, pp , 2006 [4] S.H. Choi, and Y. T. Oh, Characteristics of performance and exhaust emission of diesel engines by changes in fuel properties and application of EGR, Int. J. Automotive technology, vol. 8, pp , 2007 [5] D. Qi, M. Leick, Y. Liu, C.F. Lee, Effect of EGR and injection timing on combustion and emission characteristics of split injection strategy DI-diesel engine fueled with biodiesel, Fuel, vol. 90, pp ,

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