Effect of injector opening pressure on performance, combustion and emission

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Effect of injector opening pressure on performance, combustion and emission

  1. 1. INTERNATIONALMechanical Engineering and Technology (IJMET), ISSN 0976 – International Journal of JOURNAL OF MECHANICAL ENGINEERING 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME AND TECHNOLOGY (IJMET)ISSN 0976 – 6340 (Print)ISSN 0976 – 6359 (Online)Volume 4, Issue 1, January- February (2013), pp. 233-241 IJMET© IAEME: www.iaeme.com/ijmet.aspJournal Impact Factor (2012): 3.8071 (Calculated by GISI)www.jifactor.com ©IAEME EFFECT OF INJECTOR OPENING PRESSURE ON PERFORMANCE, COMBUSTION AND EMISSION CHARACTERISTICS OF C.I. ENGINE FUELLED WITH PALM OIL METHYL ESTER Sanjay Patil Automobile Engineering, Guru Nanak Dev Engineering College, Bidar, India, ABSTRACT This paper presents the development of computer simulation framework for prediction of performance, combustion and emission characteristics of compression ignition engine fuelled with palm oil methyl ester at different injector opening pressures. In present work, a simulation model is developed using double wiebe’s function to predict the performance of compression ignition engine. During analysis, the effect of change in injector opening pressure from 200 bar to 220 and 240 bar on engine performance, combustion and emission parameters is predicted. The engine performance is improved at injector opening pressure of 220 bar as compared to rated injector opening pressure of 200 bar. Variation of injector opening pressure to 240 resulted in inferior engine performance, combustion and emission characteristics. Highest brake thermal efficiency is observed when fuel injected at 220 bar injector opening pressure. The simulation results where brake thermal efficiency is highest are compared with that of experimental results and it is observed that simulated results are in closer approximation with experimental results. Key words: Simulation, straight vegetable oil, biodiesel, compression ignition engine, palm oil methyl ester. 1. INTRODUCTION The limited resources of fossil fuels, increasing prices of crude oil and environmental concerns have been prompted for the search of an alternative fuel to diesel oil. Among possible alternate fuels biodiesel has very high potential as it can be derived from plant species. The engine performance depends on fuel properties like viscosity, cetane number etc; engine parameters like combustion chamber geometry, compression ratio; injection parameters like fuel injection timing (FIT), injector opening pressure (IOP), rate of fuel 233
  2. 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEMEinjection, number of nozzle holes, diameter of nozzle holes, etc. Variation in IOP changes thefuel spray pattern, droplet size and droplet penetration causes the rate of evaporation, mixingof fuel air, etc, resulting variation in engine performance, combustion and emissioncharacteristics. Venkanna B.K.et.al [1] conducted experimental investigations on constantspeed diesel engine. Engine is fuelled with blend of honne oil and diesel at different IOP.Increase in IOP from 200 bar to 240 bar, resulted improvement in brake thermal efficiency(BTE) and NOx emissions and decrease in CO, HC, SO emissions. Further increase in IOP to260 bar resulted in inferior engine performance due to disturbance in fuel injection pattern. S.Satish kumar et.al [2] observed significant improvement in engine performance with blend of40% karanj oil and 60% diesel at injection pressure of 170 bar as compared to injectionpressure of 200 bar. Puhan Sukuamr et.al [3] have conducted performance test on dieselengine fuelled with linseed methyl ester (LOME) and found that engine performance withLOME was inferior compared to diesel due to its lower calorific value. They also conductedinvestigations at different injection pressure 200 bar and 240 bar. At injector openingpressure of 240 bar, BTE was higher and carbon monoxide emission was lower as comparedto preset IOP of 200 bar. GVNSR Ratnakara Rao et. al [4] used a four stroke single cylinderdiesel engine fuelled with diesel to investigate optimum injection pressure and timing. Thehighest BTE was obtained at 200 bar IOP and 11° btdc. However there was slight increase infrictional power at this condition. The experimental investigation for estimation of engineperformance is costly and timing consuming process. Hence a simulation model can bedeveloped to use as a tool to predict the engine performance at lower cost. Also the modelcan be used to study the effect of change in engine operating parameters on engineperformance, combustion and emission characteristics. A.S. Ramadhas et.al [5] developedtheoretical zero-dimensional model having single wiebe function with assumed adjustableparameters to predict the results. Rubber seed oil is considered for investigation. A computer simulation model based on First law of thermodynamics can bedeveloped using double wiebe function to take account of heat released during premixed anddiffusive phase of combustion separately and to predict the engine performance, combustionand emission characteristics at different injector opening pressures. This paper presentstheoretical investigation on effect of variation of IOP on performance, combustion andemission characteristics of diesel engine fuelled with palm oil methyl ester (POME). Duringanalysis, IOP is changed from 200 bar to 240 bar in a step of 20 bar.2. MATHEMATICAL MODELING2.1. Energy balance equation According to the first law of thermodynamics for the closed system the energybalance equation is du dQr dw (1) m = − dθ dθ dθ du dQr dw where dθ is rate of change of internal energy,dθ is rate of heat released and dθ is rateof work done. Upon simplification by considering ideal gas law and rate of heat transfer we getequation (1) as 234
  3. 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEMEdT 1 dQr hc A(T − Tw ) RT dV (2) = − −dθ mcv dθ mcv cvV dθ Where hc A(T − Tw ) the convective heat transfer between gases and cylinder wall and hc isheat transfer coefficient computed by Hohenberg equation [6]. Range-kutta fourth orderalgorithm is used to solve the above equation (2) for temperature and pressure at every crankangle.2.2 Cylinder volume at any crank angle The slider crank angle formula is used to find the cylinder volume at any crank angle[7].  r 1 − cos θ 1  L  2 V (θ ) = Vdisp  − +  2  − sin θ  2 (3)  r −1  2 2  S  where r = compression ratio, L = length of connecting rod and S= stroke length.2.3 Combustion ProcessdQr Qp θ  m p −1  θ   mp = 6.908 mp   exp − 6.908  +dθ θd θ   θ    p   p  (4) Qd θ  md −1  θ  md 6.908 md  θ   exp − 6.908   θp  θ    d    p   The heat release rate is computed with equation (4). The parameters θ p & θd representthe duration, mp & m d are shape factors and Qp and Qd represent the integrated energy releasefor premixed and diffusion combustion phases respectively. Adjustable parameters areobtained with established correlation model such that the simulated heat release profilematches closely with experimental data. The amount of heat released in premixed phase is50% of heat release due to the amount of fuel injected during ignition delay period isassumed.2.4 Ignition delay An empirical formula, developed by Hardenberg and Hase [8] is used for predictingIgnition delay in crank angle degrees.   1 1  21.2   0.63 (5)ID = (0.36 + 0.22Cm )expEA  −      RT 17190 P −12.4    where I ID = ignition delay period and EA is apparent activation energy. 235
  4. 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME2. 5 Gas properties calculation The gaseous mixture properties like internal energy, enthalpy, specific heats atconstant pressure and constant volume are obtained based on the chemical composition of thereactant mixture, pressure and temperature [7].2.6 Friction lossesTotal friction loss calculated by the equation given below [9]. C m ∗ 1000 2 (6)FP = C + 1.44 + 0.4(C m ) Bwhere FP is total friction power loss and C is a constant, which depends on the engine type,C=75kPa for direct injection engine.2. 7 NOx formation NOx formation has been predicted using procedure explained by Turns [10]. Thefollowing equation is used for computation of nitric oxide. 0 .5d [NO ]  k p Po  (7) = 2k1 f   [N 2 ][O2 ]0.5 dt  RT   u   −39370  − ∆G oT      T (k )   RT where k1 f = 1.82 ∗ 1014 e  and o k pP = e  u [N 2 ] and [O2 ] are equilibrium nitrogen and oxygen concentrations in moles.[N 2 ] = 0.21∗ P RuT[O2 ] = 0.79 ∗ P RuT2.8 Soot formation predictionThe following equation has been used for prediction of soot [11].  − Esf   dmsoot  RT  (8) = C BS ∗ φ ∗ m f ∗ P 0.5 ∗ e  u  dtwhere CBS is constant and Esf is the activation energy of the soot formation reaction.3. SIMULATION A thermodynamic model has been developed using First law of thermodynamics. Themolecular formula of diesel fuel is taken as C10H22 and for POME is approximated asC19H34O2. Suitable correlations are established between adjustable parameters of doublewiebe’s function, relative air-fuel ratio and IOP engine operating conditions, so that the 236
  5. 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEMEsimulated in cylinder pressure matches closely with experimental results. A computerprogram has been developed using MATLAB for numerical solution of the equations used inthe thermodynamic model (as described above). This model computes cylinder pressure,combustion temperature, brake thermal efficiency, brake specific fuel consumption, exhaustgas temperature and emissions like nitric oxide and soot density for neat POME (P100).4. EXPERIMENTAL SETUP AND PROCEDURE Experimental results with TV-1, stationary, single cylinder, water cooled, variablecompression ratio diesel engine developing 3.5 kW at 1500 rpm are used for modelvalidation. The engine is coupled to a water cooled eddy current dynamometer for loading.Thermocouples are used for measurement of coolant and exhaust gas temperature. An air boxwith water manometer is used to measure air flow rate and a burette is used to measure fuelflow. The cylinder pressure data is recorded by using piezoelectric transducer. The technicalspecifications of the engine and the fuel properties are given in “Table 1” and “Table 2”respectively. The IOP is varied by changing the nozzle spring tension. Table 1. Engine specifications Table 1. Fuel propertiesSl. Parameter Specification Properties Diesel POMENo (D0) (P100)1 Type Four stroke direct injection Viscosity in cst 4.25 4.7 single cylinder VCR diesel (at 30°C) engine Flash point(°C) 79 1702 Software used Engine soft Fire point(°C) 85 2003 IOP 200 bar Carbon residue (%) 0.1 0.624 Rated power 3.5 kW @1500 rpm Calorific 42000 360005 Cylinder diameter 87.5 mm value(kj/kg)6 Stroke 110 mm Specific gravity 0.830 0.8707 Compression ratio 17.5:1 (at 25°C)8 Injection timing 23 degree before TDC5. RESULTS AND DISCUSSION5.1 Effect of injector opening pressure on5.1.1 Performance Parameters "Fig." 1, 2 and 3 shows variation of brake thermal efficiency, specific fuelconsumption and exhaust gas temperature with load at different injector opening pressures.Improvement in brake thermal efficiency (BTE) and reduction in brake specific fuelconsumption (BSFC) and exhaust gas temperature (EGT) is observed with increase in IOP to220 bar. Further increase in IOP to 240 bar resulted in reduction in BTE, increase in BSFCand EGT as compared to preset IOP of 200 bar. This improvement in engine performance at220 bar is due to improvement in combustion phenomenon because of reduction in fueldroplet size, better mixing of fuel and air, etc. increase in IOP from 220 bar to 240 barresulted in deterioration of engine performance due to improper combustion. 237
  6. 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME 30 Brake Thermal Efficiency 0.46 Consumption (kg/kW-hr) 25 0.44 Brake Specific Fuel 0.42 20 0.4 (%) 15 P100 at 200 bar 0.38 P100 at 220 bar 10 P100 at 240 bar 0.36 P100 at 200 bar 0.34 P100 at 220 bar 5 P100 at 240 bar 0.32 0.3 0 0 25 50 75 100 0 25 50 75 100 Load (%) Load (%)Figure 1. Variation of brake thermal efficiency Figure 2. Variation of brake specific fuel at different injector opening pressure. consumption at different injector opening pressure. 430 Exhaust Gas Temperature 380 P100 at 200 bar 330 P100 at 220 bar (°C) P100 at 240 bar 280 230 180 0 25 50 75 100 Load (%) Figure 3. Variation of exhaust gas temperature at different injector opening pressure.5.1.2 Combustion Parameters P100 at 200 bar 0.06 Net Heat Release Rate 70 P100 at 220 bar 0.05 P100 at 200 P100 at 240 bar Peak Pressure (bar) 65 P100 at 220 (kJ/CA) 60 0.04 55 P100 at 240 50 0.03 45 40 0.02 35 30 0.01 25 20 0 0 25 50 75 100 165 185 205 225 Load (%) Crank Angle (CA)Figure 4. Variation of peak pressure at Figure 5. Variation of heat release rate atdifferent injector opening pressure. different injector opening pressure. 238
  7. 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME"Fig." 4 and 5 shows variation of peak pressure and net rate of heat release with change in injectoropening pressure. Increase in IOP from 200 bar to 220 resulted in higher peak pressure and increase innet heat rate release (NHRR) during premixed phase of combustion. This may be due to betteratomization, quick evaporation of fuel and better mixing, etc. However, increase in IOP from 220 barto 240 bar resulted in lower peak pressure and less rate of heat release during premixed phase due tounpredictable injection pattern. Further, increase in IOP from 220 bar to 240 bar resulted in lowerNHRR due to poor combustion. At very high injection pressures, injection of very small dropletshaving lesser momentum might have experienced partial suffocation by its own products ofcombustion due to loss of its relative velocity with air.5.1.3 Emission ParametersOxides of Nitrogen (ppm) 1600 5.00E-07 P100 at 200 bar 1400 P100 at 200 bar 4.50E-07 P100 at 220 bar Soot (gm/m^3) P100 at 220 bar 4.00E-07 1200 P100 at 240 bar 3.50E-07 P100 at 240 bar 3.00E-07 1000 2.50E-07 2.00E-07 800 1.50E-07 600 1.00E-07 5.00E-08 400 0.00E+00 0 25 50 75 100 0 25 50 75 100 Load (%) Load (%)Figure 6. Variation of oxides of nitrogen at Figure 7. Variation of soot density at different different injector opening pressure. injector opening pressure."Fig." 6 and 7 shows variation of nitric oxide and soot density at different injector opening pressures.It is found that increase in IOP resulted in increase in nitric oxide emissions. The soot density isobserved to be reduced from IOP of 200 bar to 220 bar and increased from IOP of 220 bar to 240 bar.6. MODEL VALIDATION 30 70Brake Thermal Efficiency (%) 65 Peak Pressure (bar) 25 60 20 55 50 P100 at 220_exp 15 P100 at 220_exp 45 P100 at 220_simu 10 P100 at 220_simu 40 35 5 30 0 25 0 25 50 75 100 0 25 50 75 100 Load (%) Load (%) Figure 8. Compression of simulated and Figure 9. Compression of simulated and experimental result of BTE. experimental result of peak pressure. 239
  8. 8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEMEModel is validated for brake thermal efficiency and peak pressure at IOP of 220 bar bycomparing with experimental results. From figures 8 & 9 it is observed that the simulatedresults are closer to experimental results.7. CONCLUSIONFrom the results of computer simulation model and experimental following conclusion aredrawn • Improvement in BTE is observed at IOP of 220 bar as compared to IOP of 200 bar. • Lower EGT at IOP of 220 bar and higher EGT at IOP of 240 bar is observed as compared to IOP of 200 bar. • Increase in IOP from 220 bar to 240 bar resulted in reduction in peak pressure and maximum rate of heat release. • Increase in nitric oxide emissions is observed with increase in IOP. • Soot density is observed to be reduced from IOP of 200 bar to 220 bar. • The simulation results are found to be in closer approximation with experimental results.8. ACKNOWLEDGEMENT I would like to express my gratitude to my Guide Dr. M. M. Akarte, National Instituteof Industrial Engineering Mumbai- India for his valuable advice and guidance throughout thiswork.REFERENCES[1] Venkanna B.K., Reddy C. Venkanna, Effect of Injector Opening Pressure on the Performance, Emissions and Combustion Characteristics of DI Diesel Engine Running on Honne oil and Diesel Fuel Blend, Journal of Thermal Science, 2010, Vol 14, No.4, Pp 1051-1061.[2] Sharma Satish kumar, Sharma Dilip, Soni S.L. and Khatri Kamal Kishore, Optimization of Injection Timing and Pressure of Stationary C.I. Engine Operated on Pre-heated Karanj-Diesel Blend, Indian Journal of Air Pollution Control, Vol IX, No1, 2009, pp79- 89.[3] Puhan Sukuamr, jegan R., Balasubbramanian K,, Nagrajan G, Effect of injection pressure on performance, Emission and Combustion Characteristics of high linolenic oil methyl ester in a DI diesel engine, Renewable Energy 34m 2009, pp142-149.[4] GVNSR Rattnakara Rao, Dr.V.Ramachandra Raju, Dr. M. Muralidhara Rao, Optimization of Injection Parameters For A Stationery Diesel Engine, Vol.2, Ver 1.0, 2010, page No.2-10.[5] A.S. Ramadhas, S. Jayaraj, C. Muraleedharan, Theoretical modeling and experimental studies on biodiesel-fueled engine, Renewable Energy 31,(2006).,1813–1826.[6] Hohenberg GF. Advanced approaches for heat transfer calculations. SAE 790825, 1979.[7] Ganesan, V., Computer simulation of Compression-Ignition engine processes, University Press(India) Ltd., Hyderabad, India, 2000.[8] J.B. Heywood, Internal Combustion Engines Fundamentals, Mc Graw Hill, 1988, ISBN 0-07-100499-8. 240
  9. 9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 1, January - February (2013) © IAEME[9] Shroff, H. D., Hodgetts, D., Simulation and Optimization of Thermodynamic Processes of Diesel Engine, SAE 740194, 1974.[10] S.R.Turns, An introduction to combustion-concepts and applications, McGraw Hill Series in Mechanical Engineering, 2000.[11] Patterson, M. A., Kong, S. C., Hampson, G. J., Reitz, R. D, Modeling the Effects of Fuel Injection Characteristics on Diesel Engine Soot and NOX Emissions, SAE Paper 940523.[12] Ramaraju. A and Ashok Kumar T V, “Biodiesel Development from High Free Fatty Acid Marotti Oil” International Journal of Mechanical Engineering & Technology (IJMET), Volume 1, Issue 1, 2010, pp. 227 - 237, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359, Published by IAEME.[13] T. Pushparaj and S. Ramabalan, “Influence of CNSL Biodiesel With Ethanol Additive on Diesel Engine Performance and Exhaust Emission” International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2, 2012, pp. 665 - 674, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359, Published by IAEME.[14] V.Narasiman, S.Jeyakumar, M. Mani and K.Rajkumar, “Impact Of Combustion On Ignition Delay And Heat Release Curve Of A Single Cylinder Diesel Engine Using Sardine Oil As A Methyl Ester” International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 3, 2012, pp. 150 - 157, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359, Published by IAEME.[15] Z. Ahmed and D. K. Mahanta, “Exergy Analysis of a Compression Ignition Engine” International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2, 2012, pp. 633 - 642, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359, Published by IAEME. 241

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