Combustion and Injection Characteristics of a Common Rail Direct Injection Diesel Engine Fueled with Methyl and Ethyl Esters

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1 Combustion and Injection Characteristics of a Common Rail Direct Injection Engine Fueled with Methyl and s Ertan Alptekin 1,,*, Huseyin Sanli,3, Mustafa Canakci 1, 1 Kocaeli University, Department of Automotive Engineering,, Izmit, Turkey Alternative Fuels R&D Center, Kocaeli University, 7 Izmit, Turkey 3 Ford Otosan Ihsaniye Automotive Vocational School, 0 Golcuk, Turkey * Corresponding Author ertanalptekin@kocaeli.edu.tr, huseyin.sanli@kocaeli.edu.tr, canakci@kocaeli.edu.tr Abstract - Biodiesel is a renewable alternative diesel fuel which can be produced from different feedstocks via different types of alcohols and catalysts. Alcohol type directly affects the fuel properties of the produced biodiesel. Different fuel characteristics may result in different performance, combustion and injection parameters in the diesel engines. Therefore, in this study, pure diesel fuel and two different s produced via ethanol and methanol were used as test fuels in a common rail direct injection (CRDI) diesel engine under five different engine loads (BMEP: 3.3,.0,.,.3 and bar) and the medium engine speed () test conditions. Detailed and comparative injection and combustion characteristics of these test fuels were investigated. According to the test results, maximum cylinder pressure and heat release of ethyl and methyl s were generally higher than those of diesel fuel. Fuel injection characteristics changed with the fuel type and engine load. Keywords - CRDI diesel engine, ethyl, methyl, combustion, injection I. INTRODUCTION Using renewable biofuels provides many advantages such as cleaner environment and economic contribution. Biodiesel is a preferred renewable biofuel which can be produced from vegetable oil, waste vegetable oil and animal fats. Using waste vegetable oils in biodiesel production is an important issue. Because many countries have a considerable amount of waste frying oil. Utilization of waste frying oils will provide lower costs in biodiesel production process and also will be a solution for the environmental problem causing from the disposal of waste frying oils. Methanol is mostly used in biodiesel production. Ethanol is another alcohol that can be used in biodiesel production as well. As well-known, the alcohol and catalyst type directly affect the fuel properties of produced biodiesel. Namely, different fuel properties may have different effects on the engine combustion, performance and injection characteristics. According to literature, comparison of ethyl and methyl s in modern diesel engines needs more investigations. Therefore, in this study, a common rail direct injection (CRDI) diesel engine was fueled with ethyl and methyl s and combustion and injection characteristics of these fuels were investigated and compared to those of pure diesel fuel. II. MATERIAL AND METHOD In the present study, diesel fuel was bought from a local gas station. In the biodiesel production process, waste frying oil was used. The waste oil was supplied from a local pastry shop. Ethyl and methyl s were produced from waste frying oil in a biodiesel pilot plant in the presence of different catalysts and alcohols according to optimum reaction parameters determined after an optimization process. Details about the biodiesel pilot plant and biodiesel production process can be found in the references [1, ]. Fuel properties of the biodiesels and diesel fuel given in Table were characterized in Alternative Fuels Research and Development Center-Kocaeli University and Marmara Research Center-The Scientific and Technological Research Council of Turkey. Property Table 1. Properties of the Test Fuels Unit Fuel Methyl Ester Ethyl Ester Ester content % Cetane number Density ( C) kg.m Viscosity ( C) mm.s Flash point C 3 3 Heating Value MJ.kg Monoglyceride % (mass) Diglyceride % (mass) Triglyceride % (mass) Free glycerin % (mass) Total glycerin % (mass) A turbocharged-intercooled diesel engine with CRDI fuel system was used in the engine tests. Details about the test engine were given in Table. A hydraulic dynamometer was used to keep the engine under different engine loads. As known, the diesel engines for passenger cars are generally used in the range of rpm (but mostly between rpm) at low or medium engine loads. Therefore, a constant engine speed () in this range and five partial engine loads (BMEP: ~3.3,.0,.,.3 and bar) were 3

2 selected for the engine tests. General view of the experimental setup was illustrated in Fig. 1. The test engine was not modified for different kinds of test fuels and factory defaults were used. Table. Specifications of the Test Engine Engine 1.9 liter, Fiat JTD Direct injection, turbocharged, Type intercooler, four stroke, water cooled, common-rail Number of Cylinder Bore - Stroke mm -. mm Compression Ratio 1.:1 Maximum Power 77 kw at 00 rpm r Maximum Brake Torque 0 Nm at 170 rpm The test engine used in this study has split injection strategy; pilot injection and main injection. The injection characteristics were given in Figs. 3 and. Pilot injections weree before top dead d center (BTDC) whilee main injections weree after top dead center (ATDC) for all test conditions. It s clear from the figure that different fuel properties of the test fuels resulted in different injection characteristics. Brake Specific Fuel Consumption (g/kwh) rpm Fig. Brake specific fuel consumption results r Fig. 1 Experimental setup The intake air mass flow was measured by AVL Flowsonix-Air product. The fuel temperature was controlled by a heat exchanger and kept at C ± 3 C. A crank angle encoder (AVL 3C) was connected to thee engine crankshaft pulley to detect the crankshaft position. A glow-plug sensor (AVL-GHP) used for diesel applications was mounted on the cylinder and AVL FlexIFEM brand product was used to obtain the cylinder pressure data. A current clamp (Fluke) was used for gettingg the injection signals. Start and end of injection timings were derivedd from the injector current. AVL IndiCom combustion analysis program wass used for obtaining and analysing cylinder gas pressure and injection timingg data. The cylinder gas pressure data of engine cycles were collected with a resolution of 0. crank angle ( CA). Due to lack of the measuring system, the rail injection pressure could not be measured. Fuel consumption wass measured by an electronic scale with a precision of 1g. Thee engine testss were repeated by threee times and the results weree averaged. III. RESULT AND DISCUSSION Brake specificc fuel consumption (BSFC)) results of thee tests fuels were shown in Fig.. BSFC valuess decreased as the engine load increased. Ethyl and methyl s had higher BSFC values than those of pure diesel fuel. The average increases in BSFC results were about.% and % % for methyl and ethyl s, respectively. Thee reason for higher fuel consumptionn of fuels was their lower heating values compared with pure diesel fuel. On the other hand, methyl and ethyl s had close BSFC values to each other. Similar results can be found in the literature [3-]. Generally, the start s of pilot injection (SPI) came near the top dead center (TDC) with increasing engine load up-to. bar and then SPI were w advanced with increasing engine load. End of pilot injection (EPI) results showed a similar trend with SPI values. EPI E timings of diesel fuel were earlier than those of methyl and ethyl s. On the other hand, EPI timings of ethyl s were obtained at later crank angles ( CA) compared with w methyl. However, pilot injection durations (PID) ( µs and crankk angle ( CA)) of methyl and ethyl s were very v close to each other. PID values of diesel fuel were higher than those off the fuels. PID duration changed slightly with w respect too engine load. The injected fuel amount (mg) perr cycle in the pilot and main injections increased with increasing enginene load. Start of the main injection (SMI) and end of the main injection (EMI) showed different characteristics with respect to engine load. SMI values were close to each e other for the fuels. SMI timings of fuels were later l than those of diesel fuel up-to engine e load of. bar. However, they were earlier than those of diesel fuel l at the enginee loads of.3 and bar. Main injection durationn (MID - µs and CA) values of fuels were lower than those of diesel fuel on average. MID values (in CA) decreased from the engine load of 3.3 bar to bar, and then they increased with increasing i engine load. Main injection amount (MIA - mg/ /cycle) values of diesel fuels weree lower due to lower fuel consumptions compared with fuels. The variations of heat release rate, cylinder pressure data and combustion results were shown in Figs. and for alll test fuels and engine conditions. Maximum combustion pressure (MCP) increased as the enginee load increased. On average, fuels have higher MCP values than those of diesel fuel whereas MCP values of fuels were closee to each other. Cylinder pressure curves have two peaks. The magnitude of thesee peaks changed with respect to the engine e load. The results showed that the locations of MCP were close to each other and significant differencess were not seen in these values.

3 Start of Pilot Injection ( o CA, BTDC) Start of Main Injection ( o CA, ATDC) End of Pilot Injection ( o CA, BTDC) 1 11 End of Main Injection ( o CA, ATDC) 11 9 Pilot Injection Duration ( o CA) 7 3 Main Injection Duration ( o CA) Pilot Injection Duration (microsecond) Main Injection Duration (microsecond) Pilot Injection Amount (mg) Main Injection Amount (mg) 0 Fig. 3 Pilot injection characteristics Fig. Main injection characteristics

4 0 - BMEP: 3.3 Bar 10 0 CA ( o CA - ATDC) BMEP:.0 Bar 10 0 CA ( o CA - ATDC) BMEP:. Bar 10 0 Combustion Duration ( o CA) BMEP:.3 Bar 10 0 Ignition Delay ( o CA) BMEP: Bar 10 0 Injection Rate (mg/ms) Fig. Cylinder pressure and heat release rate results Fig. Combustion and injection results

5 As seen from Fig., maximum heat release rate (MHRR) values of fuels were generally higher than those of pure diesel fuel. Obtained combustion results were shown in Fig. for all test conditions. Ignition delay (ID) was identified as the CA between start of main injection and mass fraction burned of % (CA - ATDC) namely start of combustion (SOC) while combustion duration (CD) is defined as the crank angle difference between mass fraction burned of % (CA - ATDC) and CA positions. SOC timings of diesel fuels were earlier at low loads (3.3 and bar), while they were later at higher load (.3 and bar) compared with fuels. Ester fuels showed similar SOC results. CA values of diesel fuels were later than those of fuels for all test conditions. These values resulted in higher CD values for diesel fuel. There was no significant change in CD values with increasing engine load. ID values showed a different trend with respect to engine load due to the changes in the pilot and main injection timings. Another important characteristic of the injection parameters is the injection rate. Injection rate values of diesel fuels were lower than those of fuels. When the fuels were compared to each other, it s seen that they had close injection rate values. IV. CONCLUSIONS Methyl and ethyl s can be made from a diverse group of biomass-based feedstocks such as waste vegetable oils and they can be used in the diesel engines without modification. According to the investigation of combustion and injection characteristics of ethyl and methyl s in a CRDI diesel engine, the following conclusions can be summarized. BSFC values increased with using methyl and ethyl. Ester fuels had close BSFC values to each other. The injection characteristics varied according to the engine load and fuel type. Generally, fuels had higher MCP and MHRR values than those of pure diesel fuel. Overall, ethyl and methyl s had similar combustion and injection behaviors. ACKNOWLEDGMENT This study was supported by the grants from Scientific Research Foundation of Kocaeli University (Project No. 0/9). REFERENCES [1] E. Alptekin, M. Canakci, H. Sanli, Biodiesel production from vegetable oil and waste animal fats in a pilot plant, Waste Management, 3, 1-, 01. [] H. Sanli, E. Alptekin, M. Canakci, Production of fuel quality ethyl biodiesel: 1.Laboratory-scale optimization of waste frying oil ethanolysis,.pilot-scale production with the optimal reaction conditions", Waste and Biomass Valorization, [3] H. Sanli, M. Canakci, E. Alptekin, A. Turkcan,, A. N. Ozsezen, Effects of waste frying oil based methyl and ethyl biodiesel fuels on the performance, combustion and emission characteristics of a DI diesel engine, Fuel, 9, 179-7, 0. [] B. Baiju, N. K. Naik, L. M. Das, A comparative evaluation of compression ignition engine characteristics using methyl and ethyl s of karanja oil, Renewable Energy, 3, 11-1, 9. [] L. Zhu, C. S. Cheung, W. G. Zhang, Z. Huang, Emissions characteristics of a diesel engine operating on biodiesel and biodiesel blended with ethanol and methanol, Science of the Total Environment,, 91-1, 0. [] A. E. Ozcelik, H. Aydogan, M. Acaroglu, Determining the performance, emission and combustion properties of camelina biodiesel blends, Energy Conversion and Management, 9, 7-7, 0. 7