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Performance and Emission Studies on a CI Engine Using Methyl Esters of Palm Oil and Waste Cooking Oil Mixture as Fuel Masimalai Senthil Kumar1,*, Tazerout Mohand2, Ndayishimiye Pascal2 1Department of Automobile Engineering, M.I.T.Campus, Anna University, Chromepet, Chennai 2Departement Systϩmes Energϩtiques et Environnement, Ecole Des Mines De Nantes, France * Email ID: msenthilk@annauniv.edu
Abstract Palm oil (PO) is considered as one of the promising feed stocks for bio-diesel production due to its low cost and good production output. However, it is in solid form at ambient temperature. Mixing PO with waste-cooking oil (WCO) helps to reduce viscosity of PO significantly. This has the potential to reduce disposal of waste cooking oil. Making esterified fuel from this mixture ofPO + WCO can be an effective method of preparing bio-diesel from waste which can be used as fuel in diesel engines. In this work refined palm oil was used as main fuel for preparing the methyl ester. Waste cooking oil was used as an inter esterification agent to reduce overall viscosity and cloud point of the blend and the ester. A single cylinder, direct injection, air cooled diesel engine was tested using neat diesel, neat PO and the methyl ester of the mixture (PO + WCO) as fuels under variable load operating conditions. Results showed increased specific fuel consumption with neatPO and methyl esters ofPO+WCO mixture as compared to neat diesel. Specific hydrocarbon and carbon monoxide emissions were significantly reduced with the methyl esters of PO+WCO mixture as compared to neat PO. The specific hydrocarbon emission was found as 2 g/kW.hr with the methyl esters of the mixture of PO+WCO and 5.2 g/kW.hr with neat PO at the maximum power output. Whereas it was 3.8 g/kW.hr. with neat diesel. The reduction in HC and CO emissions with the methyl esters of the mixture of PO+WCO was due to the better combustion of the ester as compared to neat PO. NO and NOx emissions were found higher with the methyl ester of PO+WCO as compared to neat PO due to increased cycle temperature as a result of improved combustion rate. On the whole it is concluded that methyl esters of the mixture of PO+ WCO can be used as fuel in diesel engines without modification in engine design. Top Keywords Alternative fuels, Palm oil, Waste Cooking oil, Transesterification, Diesel Engine performance, Emissions. Top | Introduction In France, generation of waste cooking oil (WCO) is enormous and it finds difficult for disposal. One way of reducing the disposal of waste cooking oil is to modify and use it as fuel in diesel engines. Palm oil (PO) is an another promising feedstock for biofuel production due to its low cost and its good production output compared to those of other vegetable oils. Palm oil due to its better fuel properties is considered as good fuel for diesel engines [1, 2]. However, it is in solid form at ambient temperature of about 20°C. Mixing palm oil and waste-cooking oil has the potential to reduce disposal of waste cooking oil. On the other side, viscosity of palm oil is improved. Making esterified fuel from this mixture (PO + WCO) can be an effective method of preparing fuel from waste which can be used as fuel in diesel engines. As a diesel engine fuel pure palm oil (PO) has most of its properties (calorific value, cetane number, etc) very close to those of diesel fuel [1, 3]. However, it has a high content in saturated fatty acid, around 50%, in which about 45% of palmitic acid and 5% of stearic acid [4, 5]. PO is in solid form at a temperature of around 30°C, due to the high melting point of its fatty acids (63°C for palmitic acid and 70°C for stearic acid). Due to these reasons, PO can not be directly used as fuel without any modification in the engine or in the fuel. |
An effective method of using vegetable oils in diesel engines is by modifying the vegetable oil in to its monoesters by transfesterification process [6, 7]. Transesterification of vegetable oils improves the viscosity and density. In addition, the cetane number is also increased. It has been reported that the performance of esterified palm oil was superior to the neat palm oil [6, 8]. The emissions of the diesel engines such as unburn hydrocarbon, carbon monoxide and smoke density were reported to be lower with esterified fuels as compared to neat fuels [9, 10], |
In this work, refined palm oil was used as the main fuel for preparing the methyl ester. Waste cooking oil collected from the restaurants was used as an interesterification agent to reduce overall viscosity of the blend as well as the ester. PO+WCO mixture was esterified in the laboratory and used. The quantities of PO and WCO were varied to obtain the best ester. It was found that the mixture of 50% of PO and 50% of WCO (by mass) resulted in more yield of methyl ester. Hence, the optimum mixture was chosen as 50% PO and 50% WCO for engine test analysis. Experiments were conducted on a single cylinder LISTER PETTER diesel engine in the constant speed mode of operation. Performance and emission parameters were obtained with neat PO and PO+WCO ester. Experimental results with diesel as the fuel have been used as the basis for comparison. |
Top Experimental Setup and Experimental Procedure A Single cylinder 4-Stroke air-cooled diesel engine developing a power output of 5 kW at 1800 rpm was used for the work. Engine details are given in table 1. The Schematic of the experimental set up is shown in figure 1. An electrical dynamometer was used for loading the engine. An orifice meter connected to a large tank was attached to the engine to make air flow measurements. An AVL shaft position encoder was used to give signals at TDC. The fuel flow rate was measured on the volumetric basis using a fuel flow meter. Chromel-alumel thermocouple in conjunction with a slow speed digital data acquisition system was used for measuring the exhaust gas temperature. An infrared exhaust analyzer was used for measuring HC/CO emissions. NO/NOx in the exhaust was measured by using a chemiluminashence analyzer. Before conducting all the experiments, preliminary analysis was made with PO and WCO to obtain the important properties like viscosity, density, calorific value etc. to find its suitability as fuel for diesel engines. The obtained results of PO and WCO were compared with diesel in Table 2. Experiments were then carried out on the engine using diesel and xneat PO as fuels to provide base line data. During the entire investigation the injection timing was optimized and set at 20° before TDC. The engine was stabilized before taking all measurements. Readings for engine speed, fuel flow, air flow, exhaust gas temperature etc. were recorded for obtaining performance parameters. Exhaust gas analyzers were calibrated before making measurements. Observations were made for NO/NOx, HC and CO to analyze the emission characteristics. Subsequently experiments were repeated with PO and the esters of the mixture of PO+WCO. The performance and emission were analyzed and compared with neat PO and neat diesel. |
Top Results and Discussion Performance The variation of specific fuel consumption with brake power output for neat PO and methyl ester of mixture of PO+WCO is shown in figure 2. The specific fuel consumption was higher with the neat PO as compared to diesel at all power outputs. This is due to poor mixture formation as a result of the low volatility, higher viscosity and density of the neat PO. However, the specific fuel consumption was lower with methyl ester of mixture of PO+WCO than the neat PO. The methyl ester of PO+WCO mixture has a lower viscosity, which results in better atomization of the fuel as compared to pure PO. No drop in maximum power was observed with the PO and methyl ester of PO+WCO mixture. Exhaust gas temperature shown in figure. 4 was higher when the load rises and it was more for the neat PO than diesel particularly at high loads. This is due to slow combustion of neat PO. The poor volatility and high viscosity of the fuels are responsible for this. The maximum temperature of exhaust gas at peak load was 5260C with the neat PO and 4880C with the methyl ester of Jatropha oil. The maximum exhaust temperature was 4960 C with diesel. Exhaust Emissions Neat PO lead to higher specific HC (hydrocarbon) emissions as compared to standard diesel operation as seen in figure4. Poor mixing with air is one of the chief reasons for this. The maximum specific HC emission was observed as 5.2 g/kW.hr with neat PO at the maximum power output of 5 kW. However, the specific HC emission was lower with the methyl ester of PO+WCO mixture as compared to neat PO. The value of specific HC was found as 2.08 g/kW.hr with the methyl ester of mixture of PO+WCO at the maximum power. Improved viscosity and density with the methyl ester of mixture of PO+WCO lead to improvement in combustion and resulted in reduced specific HC. The value of specific HC emission with neat diesel was found as 3.82 g/kW-hr at the maximum power output of 5 kW. It is interesting to see that the values of specific Total Hydrocarbons (THC) emissions with methyl ester of mixture of PO+WCO are still lower than diesel at all power outputs. The specific CO (carbon monoxide) emission level was higher with neat PO as compared to neat diesel at all power outputs except at peak load as seen in figure 5. This is due to the lower thermal efficiency with the neat PO. It may be noted that a lower thermal efficiency with neat PO will lead to injection of higher quantities of the fuel (richer fuel air mixtures) for the same power output and hence the trend of higher CO emission. It is observed from the figure 5 that the specific CO emission with methyl ester of mixture of PO+WCO is almost equal to diesel at all power outputs. It is interesting to see that the specific CO emission for the methyl ester becomes even lower than diesel at the maximum power output. Improved viscosity and density of the methyl ester of mixture of PO+WCO results in improved combustion. The improvement in physical properties avoided rich pockets formed in the cylinder and resulted in reduced specific CO emission. Figures 6 and 7 indicate that neat PO showed lower NO and NOx (nitric oxide) emission as compared to standard diesel operation. This reduction in NO emission was mainly associated with the lowered premixed burning rate of neat PO following the delay period. This was due to lower air entrainment and fuel air mixing rates with neat PO as compared to diesel during the ignition delay period. Thus the peak temperatures and hence the NO/NOx levels were lower. The rate of heat release during the premixed burning phase became lower (not shown in this paper) with neat PO as compared to diesel. As a result the peak combustion temperature has become lower with neat PO. It is seen that the methyl esters of mixture of PO+WCO resulted in higher specific NO/NOx as compared to neat PO. Improvement in the premixed combustion rate of the heat release as a result of better atomization and vaporization of the fuel lead to enhancement in combustion and raised the peak cycle temperature. Top Conclusion A single cylinder diesel engine was operated successfully on neat PO and methyl esters of mixture of PO+WCO as fuels. The following conclusions are made based on the experimental results: |
The operation of the engine is smooth on neat PO and methyl esters of PO+WCO with acceptable performance. Increased specific fuel consumption and exhaust gas temperature are observed with neat PO and methyl esters of PO+WCO at all power outputs as compared to diesel. Methyl ester of PO+WCO mixture shows improvements in specific fuel consumption and exhaust gas temperature as compared to neat PO. Significant reduction in carbon monoxide emission is found with methyl esters of PO+WCO as compared to neat PO and neat diesel. Hydrocarbon emission is higher with neat PO as compared to diesel. Significant reduction in specific hydrocarbon emission was found with methyl esters of PO+WCO mixture. Specific NOx and NO emissions are lower with both neat PO and methyl esters of PO+WCO as compared to neat diesel at all power outputs. The reduction is more significant with neat PO due to the lowest peak flame temperature.
Top Figures | Figure 1.: Experimental Setup
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| | Figure 2.: Variation of Specific fuel Consumption with Brake
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| | Figure 3.: Variation of Exhaust gas temperature with Brake
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| | Figure 4.: Variation of Total Hydrocarbon with Brake power
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| | Figure 5.: Variation of Carbon monoxide with Brake power
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| | Figure 6.: Variation of Nitric Oxide with Brake power
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| | Figure 7.: Variation of Oxides of Nitrogen with Brake power
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Table Table 1::
| | Make | LISTER – PETTER TS1 | | General Details | 4-S, CI, Air cooled, DI, open chamber, NA, Single cylinder engine | | Bore & Stroke | 95.3 mm ′88.9 mm | | Compression Ratio | 18:1 | | Rated power output | 2.8 kW at 1500 rev/min | | Injector opening Pressure | 250 bar | | Displacement Volume | 633 cc | | Fuel Injection Timing | 20° BTDC |
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