Research Paper ULTRA LOW EMISSION EXHAUST GAS RECIRCULATION SYSYTEM USING DIRECT INJECTION IN HIGH COMPRESSION IGNITION ENGINE WITH ETHANOL FUEL 1 M. Velliangiri, 2 A.S. Krishnan Address for Correspondence 1 Assistant professor, 2 Associate professor, Coimbatore Institute of Technology Coimbatore 14, India ABSTRACT This research article presented here mainly focuses on the influence of Exhaust gas recirculation (EGR) and split injections technique that was used to improve the ethanol fuel combustion in compression ignition (CI), with and without EGR system. Combustion simulation results and experimental results are investigated and compared with different experimental conditions. This research engine fuel as 95% ethanol +5% water as a fuel in a four stroke single cylinder variable compression ratio (VCR) engine. The VCR engine is used with compression ratio (28.8:1) and conducted various load conditions. Performance and exhaust emissions of NOx, CO and HC is compared with ethanol fuel split injection mode, single injection mode and diesel fuel mode. Brake thermal efficiency of pre and post injection mode was better than direct injection (DI) ethanol mode. The VCR engine operating with ethanol fuel split injection mode showed peak brake thermal efficiency (BTE) of 29%, which is nearly operating range in the baseline diesel engine. Ethanol fuel was mixed with 3% castorene R40 (lubrication oil) oil by volume due to fully soluble in alcohol fuels. It was used both air and liquid cooled engines running on methanol and ethanol fuel. Pre and post ethanol injection mode was 54.4 % reduction of oxides of nitrogen (NOx) compared with single injection mode of operation. KEYWORDS: Ethanol Direct injection; split Injection; EGR; high compression ignition; Experimental investigation. 1. INTRODUCTION Fuel energy conservation and diversification of sources of energy, which resulted from the initial price of crude oil increase in the early 2002, served as a stimulant for befoul research on all aspects of use internal combustion engines. Befoul especially ethanol and methanol, comprise one group of alternative fuels which is considered attractive for this purpose. Both ethanol and methanol can be produced from indigenous energy resources like biomass, coal and natural gas. Nowadays, the extinction usage of fossil fuel due to continuous usage becomes the focus attention for all the people in the world who depend on this energy source in every activity. The researchers attention is focused on fossil fuel due to the fact that continuously usage of this fuel believed causing environment problem i.e., air pollution and global warming. Hence IC engine researchers all over the world have been trying to look for a solution by exploring and using an alternate fuel, which is environmental friendly and sustainable availability. Compression ignition (CI) engine has higher thermal efficiency and produces higher power that can save more fuel compared to gasoline engine [1]. Therefore, diesel engines are usually used on large buses, trucks, heavy duty equipments, agricultural equipments and industrial machineries. However, diesel engines also produce gaseous pollutants such as carbon monoxide (CO), carbon dioxide (CO 2 ), sulphur oxides (SO x ), nitrogen oxides (NO x ), unburned hydrocarbons (HC), and particulate matter (pm) [1-3]. Until now diesel fuel is usually derived from fossil fuel, therefore alternative fuels are needed to replace fossil based fuels, for both reducing the consumption of fossil fuels and pollutants in the exhaust gases. 2.0 LUBRICATION Fuel Injection systems were lubricated by the fuel itself. When ethanol fuel was substituted for diesel, the lubricant must be supplied within the fuel to provide lubrication of the fuel injection pump and injector. The lubricant chosen has to be miscible with the fuel. Ethanol fuel was mixed with 3% by volume of castorene R40 was used. Castorene R40 is a Castor oil based blend incorporating synthetic lubricants and additives which enhance the castor oils, naturally high film strength and resistance to seizure. Lubrication oil was fully soluble in alcohol fuels and ideally suited for use in both air and liquid cooled engines running on methanol and ethanol fuel. Ethanol Fuel properties are shown in Table-1 Table: 1- Ethanol Fuel Properties Chemical formula of ethanol C 2 H 5 OH Molecular weight of ethanol 46.0 Composition of ethanol by weight Carbon 52.0% Hydrogen 13.0% Oxygen 35.0% Specific gravity at 15.5 o C 0.794 Boiling point o C 78.0 Latent heat of vaporization in kj/kg 900 Vapor pressure at 58 0 C in bar 0.21 Lower calorific value in kj/kg 27,880 Mixing heating value in kj/kg 2970 Stoichiometric air/fuel ratio 9.0 Ignition limit Air/ fuel ratio 3.57 to17 Self ignition temperature 420 o C Cetane number 11 Octane numbers 102 (a) For Research 111 (b) For Motor 94 3. Diesel RK simulation (Thermodynamic Tool) Diesel RK-model is used for multi fuel thermodynamic combustion simulation and predicts performance and emission parameters. DIESEL-RK is intended for calculation and optimization of the super and turbocharged internal combustion engines. Simulation tool is (version of the DIESEL-RK is 4.1.3.189 (June 2012)) different from analogues. RKmodel is used for mixture formation, combustion in different fuels in CI and SI engines and also this tool is used for multi-parameter optimization. Main features of DIESEL-RK are similar to known thermodynamic programs. It has new advanced applications which are absent in other programs.diesel combustion simulation, fuel injection simulation and optimization are used in DIESEL RK. It was used for simulation and optimization of piston bowl shape, injector design and location. Shape of injection profile and multiple injections (split injections) parameters were analyzed.
RK-model was accounted for fuel drop sizes, interaction of free sprays with swirl spray, and wall impingement, evolution of near-wall flow formed by spray, hit of fuel on cylinder head surface, hit of fuel on cylinder liner, effect of piston motion and swirl intensity on heat release rate. A precise description of the combustion process is important in modeling the formation of harmful substances in the cylinder. 3.1SIMULATIONS OF ETHANOL FUEL The multi-zone RK-model is used for ethanol fuel combustion, injection parameter optimization, fuel injection profile prediction, account of exhaust gas recirculation (EGR), temperatures of piston and cylinder head and heat release rate computation. The model allowed to prediction of heat release rate, single and split injection mode, NOx and smoke for the VCR engine. Simulation tool was used to predict pressure Vs crank angle, heat release curve, compression ratio and optimization of diesel and ethanol fuel. It can be seen that the proposed mathematical model provides a satisfactory agreement between the simulated and experimental data in a wide range and different load conditions. Fig.1 is shown injection velocity Vs crank angle profile, it is indicated that the injection velocity reaches maximum after start of injection 4 deg and duration of injection is 27 deg. From Fig.1 split injection, it is shown that injection velocity increases and decreases with crank angle. Injection velocity reaches at maximum after start of injection 3 deg and duration of injection split in to three injections. The injection quantity was divided in to three parts. Out of three pre and post injection quantity was equal and second part of injection was grater then first part. The simulation was used to predict split injection performance and injection profile. Diesel RK thermodynamic simulation tool used for predict pressure Vs crank angle diagram for ethanol fuel high pressure injection (single injection mode). From the fig.2 shows that, the combustion simulation was used for fuel injection angle before top dead center (BTDC) -15 deg and cylinder peak pressure was predicted with variable load conditions. The maximum peak pressure 128 bar was attained at after TDC 11 0. Compression ratio 28.8:1 was used for simulation and predicted in cylinder peak pressure. Fig.2. shows that the pressure Vs crank angle (Ethanol fuel mode simulation using variable injection angle before TDC 17 T0 29 Deg, CR 28.8:1, rpm - 1500) From the fig, it is shown that the combustion simulation in cylinder peak pressure was increased with increasing compression ratio with constant load conditions and fuel injection angle is varied from BTDC 17 T0 29 Deg (CR 28.8:1). The maximum cylinder peak pressure 142 bar was attained at after TDC 11 0. Pressure Vs crank angle diagram was used to predict and optimized injection angle was implemented in experimental. SPLIT INJECTION Fig: 1 Injection velocity Vs crank angle (Diesel RK software simulation - Ethanol Fuel injection profile, single injection, and split injection BP 1.1929 kw) Peak Injection velocity = 26 m/s, x axis crank angle (deg) Fig: 2 Pressure Vs Crank angle (Ethanol fuel single Injection angle of injection BTDC-15 deg -rpm 1500.) Fig: 3 Pressure Vs crank angle and Concentration of NO X (ethanol fuel single injection mode simulation results (variable compression Ratio range 22 t0 28.7)
From the Fig.3, it is shown that the in cylinder peak pressure was increased with increasing compression ratio (variable compression Ratio range 24 to 28.8:1) with constant load and speed. The maximum peak pressure 138 bar was attained at after TDC 11 0. Fig.4 shows that variable injection angle BTDC 17 T0 26 Deg- CR 28.8:1, rpm- 1500. Tt is shown that NOx was increased with increasing fuel injection angle before top dead center (BTDC 17 T0 26 Deg, CR 28.8:1) Ethanol single injection mode simulation at maximum load condition (BTDC 17 T0 26 Deg-CR 28.8:1) was started from 2000ppm to 6000ppm. It was clear that ethanol fuel single injection angle was (17 deg) optimized for reduction of NOx emission. The fig 4 shows engine parameters viz, engine bore, piston stroke, compression ratio, basic engine mechanism design data, and connecting rod length. This base data was used to simulate combustion and emission parameters. Simulation results show that NO x was increased with increasing load conditions. Ethanol fuel pre and post injection mode simulation at maximum load condition was 900 ppm. It is clear that ethanol fuel Pre and post injection mode was 54.4 % greater reduction of oxides of nitrogen than single injection mode. Pre and post injection mode was low temperature combustion to compare single injection combustion mode. It was concluded that NOx formation rate was reduced in split injection mode of operation. The Fig.5 shows that the heat release rate Vs crank angle, in which, heat release rate was increased with increasing fuel injection angle before top dead center (BTDC 17 T0 39 Deg-CR 28.8:1). It is shows that, pre and post injection heat release rate Vs crank angle simulation results. Heat release rate was split in to three peaks, first peak was at 350 deg, second peak was attained at 365 deg and third peak was attained at 385 deg. It was increased with increasing different load conditions. Fig.4.Operating mode data (simulation data sheet) and Ethanol fuel simulation results pre and post injection- rpm - 1500. Single injection Split injectio n Fig.5. Heat release Rate (j/deg ) Vs crank angle (ethanol fuel mode simulation variable injection angle BTDC 17 T0 29 deg CR 28.8:1, rpm -1500) and Heat release Rate j/deg (simulation pre and post injection) Fig.6 Heat release rate j/deg comparison of ethanol single and split injection mode simulation (angle of injection BTDC 17 CR 28.8:1) The figure 7 shows that, simulation results of single temperature combustion than single injection injection and split injection heat release rate Vs crank angle. Split injection heat release split in to three peaks, first peak was at 350 deg, second peak was attained at 365 deg and third peak was attained at 385 deg. It was increased with increasing different load conditions. Pre and post injection mode was low combustion mode and pressure Vs creank angle comparison of ethanol single and split injection. The fig 6 shows that the experimental comparison of ethanol single and split injection in-cylinder pressure. Combustion simulation data was used to predict in cylinder peak pressure. Cylinder peak pressure was
increased with single injection mode of simulation compare with split injection. The maximum peak pressure of split injection mode was 124 bar attained at after TDC 12 0. It was clear that split injection was low temperature combustion. 4.0 EXPERIMENTAL TEST AND INSTRUMENTATION The experimental engine was single cylinder variable compression ratio (VCR) engine water cooled, direct injection and modified split injection diesel engine. Single cylinder diesel engine is used throughout the world (including developing countries) for small scale power generation, grain milling, on construction sites and for pumping duties. Its rugged construction in cast iron with forged steel crankshaft and connecting rod, replaceable shell bearings and aluminum piston makes it an ideal research engine. Water cooling enables relatively easy access for temperature and pressure measurements in the cylinder. Power may be taken off either end of the crankshaft or at half speed off the camshaft. Table 2 gives the original specifications of the standard engine. 4.1 COMPUTERISED DATA ACQUISITION SYSTEM The computerized data acquisition system was used to measure and acquire in-cylinder pressure. Indicator diagrams derived from the cylinder pressure data offer detailed insight into the combustion process and allow the drawing of conclusions regarding the process of combustion. Table: 2- Research engine data Make Research engine No of cylinder One Type of cooling Water Ignition Compression ignition Bore 87.5mm Stroke 110 mm Compression ratio 17.5: 1 Speed 1500 rpm Brake power 4.9 kw Compression Ratio Diesel 17:1. Ethanol 28.8:1 4.2 PRESSURE SIGNAL Pressure transducers are widely used in engine research for acquisition of in-cylinder pressure data. For this study a Kistler - type 6123 AI (Serial No. SN 370721) air cooled piezoelectric pressure transducer was used. The small transducer output charge was converted and amplified to a pressure proportional voltage signal using a Kistler charge amplifier.which is basically a charge-voltage converter. After amplification the signal was fed into a 12 bit Analog to Digital converter which digitizes the amplitude of the measured signal. 5.0 EXPERIMENTAL SETUP The experimental setup used in this study is shown in fig.7.the experimental work was conducted on four stroke single cylinder VCR split injection setup, water cooled, and (DI) direct injection engine coupled on an eddy current dynamometer. For measuring BP, exhaust temperature, NO X, CO, CO 2 and Unburned HC level was measured in the exhaust pipe. The engine exhaust temperature was measured using digital chromel -alumel thermocouple. The NO X level was measured using NO X analyzer. The carbon monoxide and unburned hydrocarbon was measured by using infrared analyzer. Fuel consumption was measured with the help of burette and digital stop watch. The experiments were conducted at various loads from no load to full load with and without coated piston with different fuels. 6.0 ENGINE MODIFICATION The selected engine was variable compression ratio (VCR) diesel engine. The specifications and technical details of the research engine are shown in table 2. The engine is water cooled and single cylinder vertical engine. The engine is mounted on a sturdy concrete bed to withstand the dynamic forces and vibrations produced. The required compression ratio and pre and post injection setups were provided with modifications. 6.1 EXPERIMENTAL TEST DESCRIPTION The experimental engine was designed for this work was derived from the single cylinder VCR diesel engine, modified suitably to accommodated pre and post injection (split injection) electronic control module (ECU). The experiment tests were conducted using ethanol fuel and diesel fuel with the compression ratio from 17:1 to 29.4:1. The experimental results were reported and discussed. The purpose of the computerized data acquisition system was used to measure and acquire cylinder pressure. Indicator diagrams derived from the cylinder pressure data offer detailed insight into the combustion process and allow the drawing of conclusions regarding the process of combustion itself. Experimental set up was used to measuring and acquiring cylinder pressure data. It consists of a pressure transducer, a crankshaft encoder giving the basis for pressure measurements and a measuring system for storing and evaluating the pressure signals. Four different types of fuel injectors were evaluated for measured engine brake thermal efficiency as well as spray characteristics with Ethanol fuel. Fig.7. Computerized Data Acquisition System VCR Engine Experimental setup 7.0 RESULTS AND DISCUSSION The experimental and simulation results were compared and discussed various load conditions, single and split injection mode of operations. Unburned hydrocarbon (HC), carbon monoxide (CO), oxides of nitrogen (NOx), total fuel consumption (TFC), specific fuel consumption (SFC), brake thermal efficiency (BTE) of the research VCR engine operating with ethanol fuel and base line engine results were compared and discussed. The high pressure direct injection diesel mode and pre and post injection mode experimental results were compared for performance and Emissions with Coating and without coating. 8.0 UNBURNEDHYDROCARBON EMISSIONS From the fig.8 shows that it is clear that, 10% of unburned hydrocarbon emission was reduced in pre and post injection mode than ethanol fuel single mode of operation. Experimental mode ethanol (pre and post injection mode) HC emission slightly increased than simulation. Ethanol pre and post
injection with coating mode slightly decreased than without coating experimental mode. Fig.8. HC Vs BP Comparison at Constant Speed Mode ( rpm -1500 ) E SIM-Ethanol simulation, E EXP- Ethanol Experimental, DIESEL EXP Diesel Experimental mode The ethanol fuel has sufficient amount of oxygen, due to that unburned hydrocarbon (HC) emission is reduced. As a result of this, the HC will split into H and C which mixes with O 2, thereby reducing the HC emissions both pre and post injection and single injection mode. Experimental observation for diesel mode with coating is 4.2% reduced than without coating. 8.2 CO EMISSIONS In fig.9 shows that different modes of experimental and simulation results were compared and discussed. It is clear that CO was decreased with zirconia coating due to the complete combustion. The carbon monoxide, which arises mainly due to incomplete combustion. It is a measure of combustion efficiency. Generally, oxygen availability of ethanol was high, due to that carbon easily combines with oxygen and reduces the CO emission. It was observed that pre and post injection 40.2% CO emissions were less than baseline diesel engine. Diesel with coating and without coating results are compared and shown. Ethanol fuel simulation and experimental results are compared. Fig.9. CO Vs BP Comparison at Constant Speed Mode (RPM-1500) Fig.10. NOx Vs BP Comparison at Constant Speed Mode (rpm-1500) From the Fig. 10, it is shown that the NOx was increased with increased load conditions at all test conditions. Diesel injection without coating slightly decreased compare to with zirconia coating. Ethanol single injection mode with zirconia coating slightly increased with compare to without coating. Ethanol split injection mode with coating NOx emission was decreased compare to single injection with coating mode. From the fig. 10 shows that simulation of NOx range from 400 to 820 ppm. It was clear that ethanol fuel Pre and post injection mode was a 54.4 % greater reduction of oxides of nitrogen than single injection mode. In comparison of Diesel mode operation with coating is 3.8% increased than without coating. 8.3 BRAKE THERMAL EFFICIENCY From the fig.11 it is shown that brake thermal efficiency of zirconia coated ethanol fuel pre and post injection mode was 5.3% increased than single injection. Brake thermal efficiency was increased due to reduction of heat loss to surroundings from the engine. Fig.11. BTE Vs BP Comparisons of Constant Speed Mode (rpm-1500) and variable load mode. Ethanol fuel was also favorable compared to that of the baseline diesel engine. Maximum ethanol mode simulation BTE (34%) of pre and post injection mode operation was achieved. 9.0 CONCLUSION The research engine, optimized compression ratio with alcohol fuels, exceeds the performance of current conventional fueled engines, and has potential as a lower-cost alternative to the diesel. Brake Thermal Efficiency of Zirconia coated ethanol fuel pre and post injection mode is 5.3% increased then single injection mode. Emissions of NOx, CO and HC using a conventional engine were shown to be extremely low with ethanol mode VCR ethanol fuel Pre and post injection mode engine is 54.4 % greater reduction of oxides of nitrogen than single injection mode due to low temperature combustion to compare with single injection combustion mode. In comparison of Diesel mode operation, with coating is 3.8% increased than without coating. The unburned hydrocarbon emission is 10.2 % reduced in pre and post injection (with coating) than ethanol fuel single mode of operation. Pre and post injection mode was better combustion than single injection.
Brake thermal efficiency with ethanol fuel is also favorable compared to that of the baseline diesel engine. In comparison of Diesel mode operation, with coating NOx was 3.8% increased than without coating. Maximum ethanol mode BTE was 29 % of pre and post injection mode operation was achieved by experimental method. 10.0 ACKNOWLEDGMENTS The authors express their deep gratitude to the management of Coimbatore Institute of Technology for providing the necessary facilities for carrying out the experiments. The authors would like to thank in particular, beloved Correspondent Dr. S. R. K. Prasad, Secretary Dr. R. Prabhakar, and our Principal Dr. V.Selladurai who have been constantly encouraging and supporting us in this research. NOMENCLATURE BMEP Brake Mean Effective Pressure NOx Oxides of nitrogen IMEP Indicated Mean Effective Pressure LHR Low Heat Rejection engine TFC Total Fuel Consumption SFC Specific Fuel Consumption Wnet Work output BP Brake Power IP Indicated Power BTE Brake thermal efficiency ITE Indicated thermal efficiency ME Mechanical efficiency UHC Unburned Hydrocarbon CO Carbon Monoxide CI Compression Ignition PSZ Partially Stabilized Zirconia PM Particulate Matter BSFC Brake Specific Fuel Consumption E SIM Ethanol fuel simulation E EXP Ethanol fuel experimental CR Compression ratio VCR Variable compression ratio BMEP Brake Mean Effective Pressure NOx Oxides of nitrogen IMEP Indicated Mean Effective Pressure LHR Low Heat Rejection engine TFC Total Fuel Consumption SFC Specific Fuel Consumption Wnet Work output BP Brake Power IP Indicated Power BTE Brake thermal efficiency ITE Indicated thermal efficiency ME Mechanical efficiency UHC Unburned Hydrocarbon CO Carbon Monoxide CI Compression Ignition PSZ Partially Stabilized Zirconia PM Particulate Matter BSFC Brake Specific Fuel Consumption E SIM Ethanol fuel simulation E EXP Ethanol fuel experimental REFERENCES 1. 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