Combustion related vibration analysis of supercharged IDI diesel engine using beef tallow methyl ester with hydrated ethanol as an additive

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1 Combustion related vibration analysis of supercharged IDI diesel engine using beef tallow methyl ester with hydrated ethanol as an additive Ganapathi Vedulla 1 B V Appa Rao 2 and Aditya Kolakoti 3 1&3 Research Scholar, Department of Marine Engineering, Andhra University College of Engineering (A) Visakhapatnam, India, 2 Professor,Department of Marine Engineering, Andhra University College of Engineering (A) Visakhapatnam, India, Abstract: This paper is intended to evaluate the engine performance indirectly through the engine cylinder vibration analysis based on the combustion excitation. The diesel based excitation which is considered the threshold for comparison is evaluated to compare it with the combustion propensity of the new combo fuel. The vibration recordings have been collected on the cylinder head, piston slap and the foundation of the engine to analyze them in the form log-log FFT plots and time waves which amply estimate the combustion propensity with alternate fuel replacing totally the diesel fuel. In parallel, the combustion pressures have also been measured with the engine data logger which collects the pressure data from the pressure transducer and the crank angle encoder and synthesizes them to present it in the form of log-log FFT plots using off line Vast an software. The pressure plots and the time waves generated by the vibration analyzer are collated to understand the engine combustion phenomena in a lucid way. Finally after tallying, it is understood that the combustion with the new fuel (Beef Tallow methyl ester with 2% hydrated ethyl alcohol) is suitable for replacement of the petro diesel with the renewable fuel. Keywords Beef Tallow Methyl Ester (BTME); Indirect Injection (IDI) diesel engine; Vibrations; Electronically controlled secondary fuel injection; Hydrated ethanol; Combustion analysis. I. INTRODUCTION Biodiesel applications in internal combustion engines are increasing day by day due to many factors. Some of them were biodiesel which acts as a cetane improver; the molecular structure of biodiesel contains approximately 10% of oxygen which helps in improving the combustion efficiency and low particulate emissions [1-5]. Researchers and demonstrated projects have shown that biodiesel can blend into diesel fuel by any proportion and some time can be directly used. Due to higher viscosity and poor atomization the direct use of biodiesel was restricted. To reduce the viscosity of the raw oils transesterification was widely used method [6-8]. Literature on IDI engines reveals that volumetric efficiency can be improved since the valves are larger and they do not compete for space with an injector nozzle, cleaner emissions due to better mixing of fuel and air. Poor grade fuels can be used with better tolerance [9-14]. A Kolakoti and BVA Rao [15-16] examine experimentally the performance and emission characterizes of IDI supercharged engine with palm methyl ester (PME) and small quantity of coconut methyl ester (COME) and Triacetin as an additive. Results reveal that the combination of PME with COME and Triacetin yields better results in reduction of tail pipe emissions and improve thermal efficiency. M Senthil kumar et al. [17-18] studied the effect of raw and preheated animal fat oil on the performance and emissions characteristics of a single cylinder direct injection engine. Longer ignition delay with lower pre mix combustion rate and drop in peak pressures was observed with neat fat. However, preheating shows shorter ignition delay, improvement in cylinder peak pressures and combustion characteristics. John DOI : /IJRTER QAVH4 96

2 Panneer selvam and K Vadivel [19] Methyl esters of beef tallow and its blend (B5, B25, B50 and B75) with diesel fuel can be used as an alternative fuel for diesel in direct injection diesel engine without modifying the basic engine design. After exhaustive search of literature, it is evident that hydrated ethanol as an additive in fat biodiesel was not so far reported. reported. In this paper an attempt was made to test the vibration and combustion aspects of a supercharged IDI engine by using different percentages of hydrated ethanol as an additive to Beef Tallow Methyl Ester (BTME). II. BIODIESEL CHARACTERIZATION As demands for energy are increasing and fossil fuels are limited, research is directed towards alternative renewable fuels like vegetable and animal based oils. If biodiesel (methyl ester) was produced from high quality edible oils these feed stocks have high cost, which currently accounts to over 85% of biodiesel production expenses. In recent years a wide range of studies have been carried out on biodiesel production from feed stocks for low cost, which includes animal fats (beef tallow, pork lard, chicken and yellow grease) and frying oils. In this paper raw beef tallow was used for biodiesel production. Raw Beef tallow is highly viscous and mostly available in solid form at ambient temperature because of their high content of saturated fatty acids. The transesterification of beef tallow oil is taken up in the present work as shown in Figure 1.The methyl ester thus obtained from transesterification process was tested for different properties as shown in Table 1. Figure 1. Process flow chart for preparation of beef tallow methyl All Rights Reserved 97

3 Table 1. Properties of BTME in comparison with Diesel and additive ethanol. S.No Properties Diesel BTME Ethanol 1 Density at 33 0 C (kg/m 3 ) Cetane Number Calorific Value (kj/kg) Latent Heat (kj/kg) Viscosity at 33 0 C (cst) Flash Point ( 0 C) Oxygen content % weight III. EXPERIMENTAL SETUP Experimentation was conducted on a single cylinder, four stroke IDI diesel engine and the specifications are shown in Table 2. The engine was supercharged with 350Watt air blower with a heat exchanger to cooler the compressed air and a designed surge tank to store the air in the idle strokes. By super charging there was an increase of 9% power output at a constant speed of 1500 rpm. Eddy current dynamometer was used for loading the engine. The experiments started with the engine warm up for about 30 min using diesel fuel, and then, the tests were conducted at five discreet part load conditions (No load, 0.77kW,1.54kW,2.31kW & 2.92kW) by maintaining fixed rpm of In the second attempt, beef tallow methyl ester was injected through the pintle nozzle at a pressure of 142 bar and the various percentages of additive Viz. 2%,4%,6% and 8% were injected at 3bar pressure into at the suction end with a suitable electronically controlled electric secondary fuel injection system as shown in Figure 2. Combustion pressures are measured with water cooled piezo electric transducer, crank angle encoder and dedicated data logger supplied by Apex innovations, Pune, India. Vibrations are measured at three strategic positions with DC-11 vibration analyzer which gives spectral data in the form of log-log FFT plots as well as in the form of time waves taking the combustion excitation as the main source of cylinder vibration. Figure 2.Schematic diagram of Experimental test rig set All Rights Reserved 98

4 Table2.Specifications of IDI Diesel engine Engine manufacturer Bajaj RE Diesel Engine Engine type Four Stroke, Forced air and Oil Cooled No. Cylinders One Bore 86.00mm Stroke 77.00mm Engine displacement 447.3cc Compression ratio 24±1: rpm, in the absence of the clutch and Maximum net power gear box, the Hp and speed of the engine are arbitrarily fixed at 2.92kW& 1500rpm. Maximum net torque rpm Idling rpm 1250±150 rpm Injection Timings to BTDC Injector Pintle Injector Pressure 142 to 148 kg/cm 2 Fuel High Speed Diesel Starting Electric Start III. RESULTS AND DISCUSSION 3.1 Pressure Derivatives Pressure plots with a least count of one degree of crank were taken for evaluation. Figures 3 (a, b, c, d, e and f) represents the pressure derivative at maximum and 3/4 th maximum loads. Maximum pressure raise can be acclaimed for neat diesel fuel operation because of its higher calorific value in Fig.3 (a) and 3(d). Mean pressure is common for all the plots that falls around 30bar. For neat BTME and BTME with additive gives the combustion pressures which are less but the area covered under the curve is comparatively more, indicating approximate equivalent energy developed to cope up with the load on the engine. Combustion in the main chamber is prolonged and this may be reason for lifting the load and maintaining the speed in the case of BTME with additive percentage and BTME dual fuel injection. Faster combustion in the main chamber will be responsible for better torque conversion and despite lesser calorific value of the BTME and alcohol the engine operates efficiently. Diffused combustion in the main chamber entails better torque conversion because of proximate energy release on the top of the piston rather than in the pre-combustion chamber. Greater burn fractions are observed in the case of diesel with respect to crank angle where as in the case of new fuel either BTME or alcohol injected, the burn fractions are smaller with increased frequency of occurrence leading to systemized combustion. Figure 3 (a).diesel fuel at 2.92 kw Figure 3 (d). Diesel fuel at 2.31 All Rights Reserved 99

5 Figure 3 (b). BTME at 2.92 kw Figure 3 (e).btme at 2.31 kw Figure 3 (c). BTME + 2% Ethanol at 2.92 kw Figure 3 (f).btme + 2% Ethanol at 2.31 kw Figure 3(a,b, c, d, e and f). Cylinder Pressure - crank angle and its derivative comparison at 2.92 kw and 2.31 kw for diesel fuel, BTME and BTME + 2% Ethanol 3.2 Cylinder vibration measurement Vibrations are measured at three strategic points these points are vertical on top of the cylinder head, piston slap direction and on foundation. Figures from 4 to 7 represent the Log-Log FFT plots at max and 3/4 th maximum loads in vertical and piston slap direction. These plots are representatives of the actual combustion excitation. The log-log FFT curves give adequate information about the combustion taken place with different fuels. The spectral density is more in the case of diesel fuel, BTME and lesser in the case of 2% hydrated ethyl alcohol in BTME. High frequency combustion with exalted amplitude can be seen in the plots of diesel fuel touching nearly 100 db. But in the case of alternate fuel, the amplitude of high frequency vibration is limited in between 100 db and 50 db. Lesser spectral density and lower amplitude at higher frequencies prompted the author to select 2% hydrated ethyl alcohol in BTME as an alternative to the diesel All Rights Reserved 100

6 Vertical on cylinder head Piston slap direction Figure 4. Log-Log FFT (dba) analysis for the reading taken on the cylinder head in vertical direction and piston slap direction using three fuels at full load on the engine. Vertical on cylinder head Piston slap All Rights Reserved 101

7 Figure 5. Log-Log FFT (dba) analysis for the reading taken on the cylinder head in vertical direction and piston slap direction using three fuels at 3/4 th load on the engine. Vertical on cylinder head Piston slap All Rights Reserved 102

8 Figure 6. Log-Log FFT (dbv) analysis for the reading taken on the cylinder head in vertical direction and piston slap direction using three fuels at full load on the engine. Vertical on cylinder head Piston slap All Rights Reserved 103

9 Figure 7. Log-Log FFT (dbv) analysis for the reading taken on the cylinder head in vertical direction and piston slap direction using three fuels at 3/4 th load on the engine. Figures from 8 to 13 represent the time wave verses amplitude at maximum and 3/4 th maximum load. From the figures it is evident that Piston slap in the case of diesel is observed more and that is the reason the amplitude touched even more than 20 g where as in other two cases the piston slap is controlled and lesser than the amplitude 20g. Especially, in the case of 2% hydrated ethyl alcohol in BTME Fig.10.The spectral density is far lesser in the case of 2% hydrated ethyl alcohol in BTME indicating better combustion propensity even over the neat BTME. The time wave is implicit with harmonics indicating smoother combustion in the case of the selected fuel combination. Reduction of piston slap otherwise converts the energy generated into torque conversion because of which the alternate fuels can operate efficiently at all loads notwithstanding the lower heat value of the fuel. More vibration in the piston slap direction jeopardizes the functioning of the engine parts like push rods, valves. Figure 8.Time wave recorded on the cylinder head in vertical direction, piston slap and foundation of the engine at full load for diesel fuel. Figure 9.Time wave recorded on the cylinder head in vertical direction, piston slap and foundation of the engine at full load for All Rights Reserved 104

10 Figure 10.Time wave recorded on the cylinder head in vertical direction, piston slap and foundation of the engine at full load for BTME + 2% Ethanol. Figure 11.Time wave recorded on the cylinder head in vertical direction, piston slap and foundation of the engine at 3/4 th load for diesel fuel Figure 12.Time wave recorded on the cylinder head in vertical direction, piston slap and foundation of the engine at 3/4 th load for BTME. Figure 13.Time wave recorded on the cylinder head in vertical direction, piston slap and foundation of the engine at 3/4 th load for BTME + 2% All Rights Reserved 105

11 3.3 Pressure variation and time wave compilation The plots 14 (a, b &c) represent matching of the vibration acceleration recorded on the cylinder head in vertical direction in the same time duration of the crank angle to investigate the combustion propensity with the all the fuels tested. It can be observed asymmetric variation of time wave about abscissa in the Fig.14(a) representing diesel combustion. The amplitude rise is unequal on both sides of the abscissa. On the positive side the amplitude has risen up to 10G and on the negative side it has reached down to 6 or 7 G. This is an indication of improper torque conversion of the energy generated. The density of the time wave is also more indicating rough combustion consisting of lesser number of harmonics. It can be observed in the Fig.14(b) same torque conversion trend similar to the diesel fuel but the curve is smooth with lesser combustion noise. In the Fig.14(c) which represents 2% hydrated ethyl alcohol in BTME, the curve is almost symmetric with better torque conversion. There is maximum pressure retention for longer duration of time. Same trend of combustion can be observed in the case of next lower part load also as seen in the Fig.15 (a, b & c). Figure 14(a). Figure 14(b). Figure 14(c). Figure 14 (a, b & c). Cylinder vibration acceleration - time wave in vertical direction and combustion pressure variation as an excitation at full load for the three fuels All Rights Reserved 106

12 Figure 15(a). Figure 15(b). Figure 15(c). Figure 15 (a, b & c). Cylinder vibration acceleration - time wave in vertical direction and combustion pressure variation as an excitation at 3/4 rth load for the three fuels tested IV. CONCLUSIONS AND RECOMMENDATIONS The following test data has been verified and the conclusions have been drawn. Test data: 1. Pressure differential curves 2. Log Log FFT curves collected on the strategic points on the cylinder head and on the piston slap direction. 3. Time waves collected on the cylinder head in the vertical direction on the cylinder head, piston slap direction and on the foundation. 4. Pressure and time wave collation to verify the heterogeneity of combustion. The pressure differential curves define smoother combustion in the case of 2% hydrated ethanol plus biodiesel. The log- log FFT curves elucidate reduced level of amplitude at higher frequencies. The time waves in the piston slap direction in the case of new combo fuel indicate lesser energy spending and higher torque conversion. Finally, the pressure - time wave collation envisages better understanding of heterogeneity reduction in the case of new renewable All Rights Reserved 107

13 Finally it is understood that the new fuel entailing the combination of BTME and 2% hydrated alcohol is adjudged as the suitable renewable fuel to replace the diesel fuel with slight changes like the introduction of secondary injection of the additive at the suction end and super charging with appendages like heat exchanger and surge tank in between the engine and the super charger. REFERENCES I. Sharma. Y.C, Singh. B, Development of biodiesel from karanja, a tree found in rural India. Fuel 2007; DOI: /j.fuel II. Sharma. Y.C, Singh. B, Upadhyay. S.N, Advancements in development and characterization of biodiesel. A review. Fuel 2008; 87; pp III. Ramadhas. A.S, Jayaraj. S, Muraleedharan. C, Biodiesel production from high FFA rubber seed oil. Fuel 2005;84; pp IV. Sahoo. P.K, Das. L.M, Babu. M.K.G, Naik. S.N, Biodiesel development from high acid value polanga seed oil and performance evaluation in a CI engine. Fuel 2007; 86; pp V. Agarwal. A.K, Biofuels (alcohols and biodiesel) applications as fuels for internal combustion engines. Prog Energy Combust Sci 2007; 33; pp VI. Burr. M, Gregory. C, Vehicular exhaust. Encylopedia Environ Health 2011; 49; pp VII. Kolakoti. A, Rao. B.V.A, A comprehensive review of biodiesel application in IDI engines with property improving additives. I-manager s J Mech Eng. 2015;5(4); pp VIII. Rao. P.S, Gopalakrishnan. K.V, Vegetable oils and their methylesters as fuels for diesel engines. Indian J Technol 1991;29(6); pp IX. Talamala. V, Kancherla. P.R, Appa Rao Basava. V, Kolakoti. A, Experimental investigation on combustion, emissions, performance and cylinder vibration analysis of an IDI engine with RBME along with isopropanol as an additive. Biofuels Available from: / X. RamanaMurty Naidu. S.C.V, Appa Rao. B.V, kolakoti. A, Performance and emission analysis of an indirect injection diesel engine operated with palm methyl ester (PME) and 1, 4-Dioxane Additive Blend. Int J Eng Res Technol. 2015;4(4); pp XI. Prasad rao. K, Appa Rao. B.V, Performance and emission characteristics of an indirect diesel injection engine fueled with Mahua methyl ester and methanol as an additive. Biofuels. 2014;5(4); pp DOI: / XII. Prasada Rao. K, Victor Babu. T, Anuradha. G, et al. IDI diesel engine performance and exhaust emission analysis using biodiesel with an artificial neural network (ANN), Egypt. J Petrol Available from: /j.ejpe XIII. GanapathiVedulla, Aditya kolakoti, Appa Rao. B.V &SantoshBabji. P, Performance and Emission study of supercharged IDI diesel engine using Beef Tallow Methyl Ester with ethanol as an additive. International Journal of Scientific Research and Management 2017; 5(7); pp XIV. DOI: /ijsrm/v5i7.12 XV. S C V RamanaMurty Naidu, B V Appa Rao and Aditya Kolakoti, Experimental Investigations on Combustion and Vibration Analysis of an Indirect Injection Diesel Engine fuelled with palm methyl ester (PME) and 1,4- Dioxane as an additive, International Journal of Informative & Futuristic Research 2015; 2 (8), pp XVI. Aditya Kolakoti &Appa Rao.B.V, Effect of fatty acid composition on the performance and emission characteristics of an IDI supercharged engine using neat palm biodiesel and coconut biodiesel as an additive. Biofuels 2017; DOI: / XVII. Kolakoti.A&Rao. B.V.A System and method for a supercharged IDI diesel engine run by biodiesel. Indian Patent 2017; Patent number ,pp XVIII. Senthil Kumar. M, Kerihuel.A,Bellettre.J and tazerout.m, A Comparative study of different methods of using animal fat as a fuel in a compression Ignition engine. Journal of Engineering for Gas Turbines and Power 2006;128;pp XIX. SenthilKumar.M, Kerihuel.A,Bellettre.J and tazerout.m, Investigations on the use of preheated animal fat as fuel in a diesel engine. Renewable Energy 2005; 30(9); pp XX. John PanneerSelvam.D and Vadivel.K, Performance and emission analysis of DI diesel engine fuelled with methyl esters of beef tallow and diesel blend. Procedia Engineering 2012; 38; pp All Rights Reserved 108