National Conference on Advances in Mechanical Engineering Science (NCAMES-2016)

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1 Effect of Compression Ratio on the Performance and Emission Characteristics of a Direct Injection CI engine fuelled with Pongamia biodiesel blends Srinath Pai 1, Shrivathsa 2, Dr. Abdul Sharief 3, Dr. Shiva kumar 4, Dr. Shreeprakash B 5 1 Associate Professor, Dept of M.E, Srinivas School of Engineering, Mangalore , Karnataka, India 2 Student, Dept of M.E, Srinivas School of Engineering, Mangalore , Karnataka, India 3 Professor and Principal, P.A.College of Engineering, Mangalore , Karnataka, India 4 Associate Professor, Dept of M.E, MIT, Manipal , Karnataka, India 5 Principal, S S E, Mukka,Mangalore , Karnataka,India. Abstract Diesel engine has got a lot of advantages while compared to petrol engines like high power production with less fuel consumption, higher thermal efficiency etc. The diesel engine is best fitted for all the heavy vehicles and also it can be used for army, marine, navy applications. The experiment is conducted on a single cylinder, four stroke CI engine fuelled with different blends of Pongamia biodiesel and the outcomes are compared with the diesel. The effect of compression ratio on the performance and emission parameters of the engine is analysed. The SFC is found higher for biodiesel blends as compared to diesel. The BTE for biodiesel is found higher than the diesel. It is found that the HC emission decreases as the compression ratio increases and the NOx and CO emissions increase with the gains in the compression ratio. The theme of this work is to assess the effect of injection timing on biodiesel fueled diesel engine combustion and exhaust emissions. Keywords Compression ratio, Biodiesel, Performance, Emission. I. INTRODUCTION The depletion of fossil fuels and environmental degradation has motivated researches to consolidate the use of biofuels for internal combustion engine applications. Biofuel is a clean burning fuel produced from natural, renewable energy resource, it operates in CI engines similar to the petroleum diesel.number of researches have been done on the commercial CI engines run by different biodiesel blends and concluded that upto 20% of biodiesel can be used in existing engines without any engine modification. But, high viscosity and low volatility are the problems with biodiesels. Therefore, by altering the engine parameters such as Compression Ratio, Injection Timing and Injection Pressure, it is found that the performance and emission characteristics of the engine can be improved. The compression ratio is the quantity that denotes how much the charge is compressed by the piston during the compression stroke of the engine. The compression ratio is the proportion of total volume of the cylinder to the clearance volume of the cylinder. The compression ratio plays an important character in the performance characteristics of the engine. This paper deals with outcomes of varying Compression Ratio on engine performance characteristics such as Specific Fuel Consumption (SFC), Brake Thermal Efficiency (BTE) and emission parameters (such as HC, CO and NO X ). II. LITERATURE REVIEWS An easy way to comply with A number of research papers and studies have been conducted to ascertain the effect injection timing on power, performance and fuel consumption and exhaust emissions of a diesel engine fuelled with biodiesel. Number of reviews has been taken below to endorse the present study. Vijay Kumar Attri et al[1], have experimented on single cylinder, four stroke, VCR (Variable Compression Ratio) Diesel engine. They operated the engine at five different load conditions at compression ratios of 18, 17 and 16. The engine speed was set for 1500 rpm. They investigated on different performance characteristics namely Brake thermal efficiency (BTE), Brake specific fuel consumption (BSFC) and Exhaust gas temperature (EGT). They found the best performance characteristics for compression ratio of 17. They found that NOx decreases as CR increases. R Silambarasan et al[2], conducted the experiment on single cylinder Variable Compression Ratio (VCR) Engine with different blends of Annona Methyl Ester (AME) as fuel. The performance characteristics such as specific fuel consumption and brake thermal efficiency were compared with diesel fuel for various compression ratios of 16.5, 18.5 and They found that ISSN: Page 327

2 compression ratio of 19.5 for A20 blended fuel shows better performance and lower emission level. S Ananthakumar et al [3], have conducted experiments on a single cylinder four stroke variable compression ratio engine. Their study deals with performance, combustion and emission characteristics of the engine. The engine was fuelled with diesel and waste plastic oil blends. They tested three blends 2.5, 7.5 and 12.5 % in variable compression ratio engine. Waste plastic oil blend, pure plastic oil and diesel were considered for comparison. Their study reveals that brake thermal efficiency increases for all the blends when compression ratio increases from 12 to 20. The specific fuel consumption of the blends and plastic oil were higher than the diesel. But the brake thermal efficiency for all the blends, plastic oil was comparatively lower than that of diesel. M Santhosh et al [4], have experimented on a four-stroke, naturally aspirated, single cylinder DI diesel engine. They investigated the influence of compression ratio of the engine on the performance and emission characteristics of ethanol diesel blended fuel and the results compared with diesel. They carried out the test using three different compression ratios (CR 16.5, 14.3, and 12.6) at 40 and 60 % of maximum engine load. They found that at higher CR, the brake thermal efficiency (BTE) increases. Perminderjit Singh et, al [5], in their study, have experimented on a single cylinder four stroke variable compression ratio multi fuel engine fuelled with different blends of rice bran oil methyl ester and ethanol. The results are then compared with the diesel fuel. The engine was made run at a constant speed of 1500 RPM and at 50% load conditions. Experiment was carried out at different compression ratios of 17, 17.5, 18 and They found that, B15E3 gives a better decrease in BSFC than diesel as the compression ratio increase. The compression ratio of 18 was found to be the best for all the blends in terms of BTE. Srinath Pai et, al [6], conducted the experiments on a 4 stroke SI engine fuelled with 5%, 10%, 15% and 20% of ethanol blend with petrol, for compression ratios of 5:1, 6:1, 7:1 and 8:1. They experimented for various loads of 25%, 50%, 75% and full load. They found higher mechanical efficiency and volumetric efficiency for 15% ethanol blend and compression ratio of 8:1. The specific fuel consumption is found lower for 12% for ethanol blend and at compression ratio of 8:1. Devaraj J et al [7], conducted the experiments on single cylinder direct injection diesel engine powered by waste plastic pyrolysis oil blended with diethyl ether. They conducted the experiments with different compression ratios of 15, 16, 16.5 and 17 at various load conditions with a constant speed of 1500 rpm. Brake thermal efficiency was slightly higher with respect to diesel fuel. They observed that the exhaust emissions are significantly decreased with increase in diethyl ether waste plastic pyrolysis oil (DEE WPPO) at full load conditions. By increasing the compression ratio from 15 to 17, produces lower smoke opacity, hydro carbon (HC), Oxides of nitrogen (NOx) and carbon monoxide (CO) respectively. III. EXPERIMENTAL SET UP AND TEST PROCEDURE Experiments were carried on a KIRLOSKAR AV1 model water cooled 5 HP diesel engine. The engine is provided with facility to change the compression ratio. Thermocouples are provided at appropriate positions to record the temperatures. The experiments were conducted on a direct injection CI engine fuelled with Pongamia biodiesel blends for various loads by varying compression ratio (CR) from 14.5, 15.5 and 16.5 at standard injection pressure of 200bar and the standard injection timing of 20.5 o BTDC. Then the results are compared with pure diesel fuel. The engine is connected to an eddy current dynamometer to measure the load. The performance characteristics like Specific fuel consumption (SFC), Break thermal efficiency (BTE) and Exhaust Gas Temperature (EGT) were analysed. Emission characteristics like HC, CO and NOx were evaluated. The engine specifications are as follows: Table I Engine Specification SL. Engine Parameters Specification NO 1 Engine Type AV1(Kirloskar ) 2 Number of cylinders Single cylinder 3 Number of strokes Four stroke 4 Rated power 5 HP 5 Bore 80 mm 6 Stroke 110mm 7 Compression Ratio VCR( ) 8 Rated Speed 1500 rpm 9 Dynamometer Eddy current 10 Type of cooling Water cooling 11 Injection Pressure 200 bar Fig. 1 Engine Test rig. ISSN: Page 328

3 IV. RESULTS AND DISCUSSIONS The results obtained from the experiments are tabulated and plotted in the form of charts, as follows A. Performance Parameters Brake thermal efficiency v/s load increase, results in delay period decrease and biodiesel blended fuel, contains more oxygen, which increases combustion rate and improves the Brake thermal efficiency. Brake specific fuel consumption v/s load Fig. 2 BTE v/s load for CR14.5, 15.5&16.5 (Diesel) Fig. 6 BSFC v/s load for CR14.5, 15.5&16.5 (Diesel) Fig. 3 BTE v/s load for CR14.5, 15.5 &16.5 (B10) Fig. 7 BSFC v/s load for CR14.5, 15.5&16.5 (B10) Fig. 4 BTE v/s load for CR14.5, 15.5 &16.5 (B20) Fig. 8 BSFC v/s load for CR14.5, 15.5&16.5 (B20) Fig. 5 BTE v/s load for CR14.5, 15.5 &16.5 (B30) The data reported in Fig. 2, Fig. 3 and Fig. 4 show that, for all fuels increase in BTE with increase in CR 14.5 from 16.5, among all blends and diesel, BTE of B20 is found maximum, 36.3% for full load at CR16.5. The combined effect compression ratio Fig. 9 BSFC v/s load for CR14.5, 15.5&16.5 (B30) As demonstrated in Fig. 5, Fig. 6 and Fig. 7 for diesel, B10 and B20 show that BSFC decreases with CR. It was least and economical for B20 ( kg/kw-hr). Fig. 8 reported that, for B30, BSFC was found increased and for full load it was recorded kg/kw-hr. This may be due to increased compression ratio; the unused air would be much ISSN: Page 329

4 more hence poor atomization and improper combustion with increased fuel consumption. B. Emission Parameters CO v/s load high temperature of fuel air because of high swirl intensity CO emissions are decreased, whereas lower compression ratio, due to high dilution of charge with residual gases and low temperature of fuel air and less swirl intensity increases the CO emissions. Due to too much swirl at 16.5 and more volatility in B30 may lead improper combustion and increased the CO emissions. HC v/s load Fig. 10 CO v/s load for CR14.5, 15.5&16.5 Fig. 14 HC v/s load for CR14.5, 15.5&16.5 Fig. 11 CO v/s load for CR14.5, 15.5&16.5(B10) Fig. 15 HC v/s load for CR14.5, 15.5&16.5(B10) Fig. 12 CO v/s load for CR14.5, 15.5&16.5(B20) Fig. 16 HC v/s load for CR14.5, 15.5&16.5(B20) Fig. 13 CO v/s load for CR14.5, 15.5&16.5(B30) Fig.10 to Fig. 14 represents variation in CO emission v/s load. It was noted that, with the increase in CR the CO emission are decreased due to better combustion. At higher compression ratio, due to less in dilution of charge with residual gases and Fig. 17 HC v/s load for CR14.5, 15.5&16.5(B30) ISSN: Page 330

5 As illustrated, Fig 14 to Fig 17 shows variation in HC emission v/s load, it was noticed that, more HC emission was observed for neat diesel and B30 blend, whereas minimum emission was observed for the B20 blend as similar with CO emission. This may be due to B20 blending and increase in CR combination may support more proper combustion. From Figure 17, the maximum HC emission was observed for B30 may be due to an improper combination due B30 blend may retard the automation rate, so the drop in combustion rate led to increase in HC. NOx v/s load Fig. 18 NOx v/s load for CR14.5, 15.5&16.5 Fig. 19 NOx v/s load for CR14.5, 15.5&16.5(B10) Fig. 20 NOx v/s load for CR14.5, 15.5&16.5(B20) Fig. 18 to Fig. 21 describes the variation of NOx emissions with load for CR 14.5, 15.5 and 16.5, it was recorded that, minimum NOx emissions was observed for neat diesel and maximum for B20. Fig. 21 NOx v/s load for CR14.5, 15.5&16.5(B30) This may be due to biodiesel combustion have higher reaction temperatures than petroleum diesel combustion. It was also noted that lesser CR results in low NOx, even for all biodiesel. Meanwhile, NOx increase found with increasing CR. Hence CR increases both pressure and temperature, maybe the other potential causes of the NOx increase. Further, it could be concluded that, due to the combined result of both factors discussed above, may results in high NOx formation. However, more elaborated studies in the formation NOx are needed to reach explicit conclusions. V. CONCLUSIONS The following conclusions could however be proposed from the present work: Increase in the CR decreases delay period results in higher pressure and temperature, results in better automisation. Meanwhile, a more complete combustion caused by the increased oxygen content and the absence of aromatic content in biodiesel in the flame coming from the biodiesel molecules has been pointed out as the main reason for better combustion. However, increased NOx could result due to the combined effect of increased CR and biodiesel blending might increase the rate of pressure and temperature rise during the combustion processes due to better atomization, swirl and more oxygen content present in the fuel increases the burning on temperature. The major conclusions of this study are improved performance and emission was discovered due to better combustion. REFERENCES [1] H. Yogish, K. Chandarshekara and M. R. Pramod Kumar, A study of performance and emission characteristics of Vijay Kumar Attri, Vijay Kumar Sharma, Saurabh Kumar Singh, Manish Saraswat, Effect of Compression Ratio on Performance and Emissions of Diesel on a Single Cylinder Four Stroke VCR Engine, International Journal of Emerging Technology and Advanced Engineering, ISSN: , volume 5, special issue 1, April Pg. no: [2] R. Silambarasan, R. Senthil, G.Pranesh, P. Mebin Samuel, M. Manimaran, Effect of Compression Ratio on ISSN: Page 331

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