Effect of ignition delay (ID) on performance, emission and combustion characteristics of 2 methyl furan unleaded gasoline blends in a MPFI SI engine

Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2 Methyl Furan Unleaded gasoline blends in a MPFI SI engine Alexandria Engineering Journal (2017) xxx, xxx–xxx[.]

Alexandria Engineering Journal (2017) xxx, xxx–xxx H O S T E D BY Alexandria University Alexandria Engineering Journal www.elsevier.com/locate/aej www.sciencedirect.com ORIGINAL ARTICLE Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2-Methyl Furan-Unleaded gasoline blends in a MPFI SI engine Harish Sivasubramanian Department of Mechanical Engineering, Velammal Engineering College, Chennai, India Received 29 August 2016; revised November 2016; accepted 15 December 2016 KEYWORDS Furans; Oxygenates; Carbon monoxide; Hydrocarbons; Emissions; Combustion Abstract The major issue faced today is the atmospheric pollution by the gases released by vehicles 2-Methyl Furan (MF) is one such promising alternative that has potential to serve the purpose The main objective of this experiment was to investigate the effects of adding MF in a four-stroke MPFI SI engine in terms of its performance, emission and combustion characteristics Unleaded gasoline (UG) along with concentrations of MF (M10, M20 and M30) blended with UG were used as test fuels The tests were conducted at a constant load of 20 N m with the speed ranging from 1400 to 2800 rpm with an increment of 200 rpm When the blend percentage increased there was a decrease in CO and HC emissions with an increase in the BTE and NOx emissions The curve for the pressure and the maximum rate of heat release shifted towards left reducing the ignition delay with the addition of blends When the ignition timing was retarded slightly by 2°Crank Angle (CA) to counter the NOx, the BTE and NOx emissions were comparatively lesser as expected On the other hand, CO and HC emissions showed a gradual rise and maximum value of peak pressure and heat release occurred little later Ó 2016 Faculty of Engineering, Alexandria University Production and hosting by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Introduction Currently, the global concern among the researchers is the atmospheric pollution which is caused as a consequence of vehicular and industrial emissions The noxious and detrimental gases have adverse effects on all living beings The science E-mail addresses: harishsivasubramanian23@gmail.com, sharish2395@ gmail.com Peer review under responsibility of Faculty of Engineering, Alexandria University of air pollution mainly deals with predicting the concentrations and their adversities on the environment Over the past halfcentury, scientists have learned much more about the causes and impacts of air pollution [1] The key elucidation to this subject is the use of alternatives which include hydrogen, natural gas, alcohols, ethers, etc Among the alternatives, oxygenates have proven their potential without any compromise in power Gravalos et al [2] studied the emission characteristics of a single-cylinder, SI engine operating on lower-higher molecular mass alcohol blended gasoline fuels The concentrations of http://dx.doi.org/10.1016/j.aej.2016.12.014 1110-0168 Ó 2016 Faculty of Engineering, Alexandria University Production and hosting by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Please cite this article in press as: H Sivasubramanian, Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2-Methyl FuranUnleaded gasoline blends in a MPFI SI engine, Alexandria Eng J (2017), http://dx.doi.org/10.1016/j.aej.2016.12.014 H Sivasubramanian Nomenclature UG M10 M20 M30 MPFI SI O/C H/C BTE 100% unleaded gasoline 10% 2-methyl furan + 90% unleaded gasoline 20% 2-methyl furan + 80% unleaded gasoline 30% 2-methyl furan + 70% unleaded gasoline multi-point fuel injection spark ignition ratio of elemental oxygen to elemental carbon ratio of elemental hydrogen to elemental carbon Brake Thermal Efficiency methanol, propanol, butanol and pentanol were kept constant at 1.9%, 3.5%, 1.5% and 1.1% respectively The concentration of ethanol was varied (7%, 12%, 17%, 22%) and the remaining was unleaded gasoline There was 20.4% decrease in HC emission between unleaded gasoline and blend with 17% ethanol The HC emissions decreased with the increase in speed and CO emission decreased with increase in ethanol In another experiment, higher molecular mass alcohols were removed and experiment was carried out with lower molecular mass alcohols The lower mass alcohols emitted comparatively lower NOx and CO2 emission and higher CO emissions than higher molecular mass alcohols Elfasakhany and Mahrous [3] had assessed the performance and emission characteristics of n-butanol-Methanol-Gasoline blends in a SI engine They found that dual alcohols at lower blend percentage showed higher CO and UHC emissions compared to single alcohol and gasoline blend When the volumetric content was increased to 10%, the engine performance was improved and the exhaust emissions were higher They had concluded that single alcohol should be used at lower blending percentages and dual alcohol should be used at higher blending percentages Wang et al [4] have investigated the PM composition and soot oxidation in a 1-cylinder spray guided DISI engine with thermo gravimetric analysis (TGA) technique The PM emissions mainly consisted of volatile compounds rather than soot even at high engine load operation The soot from oxygenated fuels was oxidised easily than gasoline indicated by activation energies As the load increased, the activation energy and temperature needed to oxidise soot increased, indicating that it is difficult to oxidise soot if it is formed at higher temperature Lee et al [5] had investigated the performance and emission characteristics of a SI engine fuelled with DME blended LPG fuel It was found that higher DME percentages had decreased the engine torque and increased the BSFC of the engine In addition to that, the HC and NOx emissions were increased slightly with blended fuels at lower engine speeds They also found that the knock occurrence area had increased substantially with higher blending percentage of DME Song et al [6] compared the effects of MTBE with ethanol (EA) and their emissions in SI engine The acetaldehyde emissions were the same for both fuels at lower speed whereas MTBE had higher emissions than EA at higher speeds When the emissions were regulated, then EA had better performance than MTBE, but the effects were reversed at unregulated emissions Hsieh et al [7] studied the performance and emissions of ethanol-gasoline blends on SI engines The torque and BSFC CA HRR HC CO CO2 NOx aTDC BSFC NO Crank Angle heat release rate hydrocarbon carbon monoxide carbon dioxide oxides of nitrogen after top dead center brake specific fuel consumption nitric oxide were found to increase with ethanol addition There was a drastic decrease in the CO and HC emissions as a consequence of complete combustion There was a rise in CO2 level with ethanol addition which infers good combustion quality Shenghua et al [8] studied the performance, emission and combustion characteristics of a 3-cylinder port fuel injected SI engine with methanol-gasoline blends It was found that the power and torque decreased with methanol-gasoline blend CO and HC emissions also decreased and the NOx emission had changed slightly HC emissions were reduced more than 50% for the first few seconds of cold-start and nearly 30% for the remaining time CO had reduced by 25% when fuelled with M30 The start of combustion was advanced due to the methanol addition and on the other hand the rapid burning phase became shorter The thermal efficiency of methanol blends was higher due to its higher laminar flame propagation It was concluded that the engine was stable when methanol blends were lower in gasoline Elfasakhany [9] investigated SI engine fuelled with hybrid iso-butanol/gasoline fuel blends At lower speed, the CO and UHC emissions were reduced by 30% and 21% respectively for iB10 compared to gasoline The CO emissions were found to decrease till a speed of 2900 rpm and the trend began to increase thereafter above 2900 rpm Such characteristics depicted the reduced availability of combustion time at higher speeds Wang et al [10] have compared the combustion and emission characteristics of MF with gasoline, DMF and ethanol in a single-cylinder, DISI engine Experiments were conducted at stoichiometric airfuel ratio with engine speed of 1500 rpm and loads between 3.5 and 8.5 bar IMEP MF consistently produced higher indicated thermal efficiency by some 3% compared to gasoline and DMF MF can even be used in higher compression ratio SI engine because of its better knock suppression Among the four studied fuels, MF had a much faster burning rate, which makes its combustion duration the shortest At 8.5 bar IMEP, MF was about 7, and CAD shorter than gasoline, ethanol and DMF respectively The peak pressure value was the highest for MF and it produced 73% and 40% less HC emissions than gasoline and DMF respectively NOx, on the other hand had increased significantly Wei et al [11] experimentally investigated on the combustion and emission characteristics of 2-methyl furan and gasoline blended fuel in SI engine It was found to produce a higher peak pressure and higher temperature than gasoline It had higher knock resistance and thus can be used in various compression ratios of SI engine The HC and CO were reduced to a significant extent The blend M10 has produced a 10.3% Please cite this article in press as: H Sivasubramanian, Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2-Methyl FuranUnleaded gasoline blends in a MPFI SI engine, Alexandria Eng J (2017), http://dx.doi.org/10.1016/j.aej.2016.12.014 Effect of Ignition Delay (ID) lower HC emissions and 2.4% lower CO emission than gasoline It had more NOx emissions and it varied exponentially with in-cylinder combustion temperature Al-Hasan [12] has investigated the effects of ethanol addition in a SI engine and analysed the engine performance and exhaust emission Ethanol was blended in 10 different concentrations ranging from 0% to 25% ethanol with 2.5% increment It was observed that the performance of engine had risen, increasing the engine power and BTE by 8.3% and 9% respectively There was a decline in HC and CO emission by 24.3% and 46.5% respectively accompanied by an increase in CO2 by 7.5% It was summarised that 20% ethanol and 80% unleaded gasoline gave the best outcome for engine performance and exhaust emissions Lan-bin Wen et al [13] studied the effects of adding DMC and ethanol in a SI engine at a constant load of N m CO emissions decreased approximately by 68%, 61% and 2% respectively for D5, D10 and D15 respectively HC emissions decreased till a speed of 5000 rpm and after which the trend increased due to the reduced availability of combustion time at 6500 and 8000 rpm The trend of CO2 and NOx emission was opposing to that of CO emission where the trend increased with the addition of DMC The fuel consumption on the other hand had increased with DMC addition as it had a lower calorific value Karavalakis et al [14] examined the effects of ethanol and iso-butanol blended fuel on the gaseous and PM emissions from passenger cars with DISI engines equipped with wall-guided and spray-guided As the alcohol content increased, the THC and NMAC emissions decreased CO emissions were the lowest for E20 which was ascribed to the fuel-bound oxygen It was found that by increasing the ethanol and butanol blend level, the average PM mass, PN and soot mass emissions decreased Gu et al [15] experimentally studied the emission characteristics of a port fuel-injected SI engine fuelled with gasoline and nbutanol in combination with EGR When the blend percentage increased, the specific NOx, CO and HC decreased When the spark timing was advanced, there was an increase in engine specific HC, NOx and PN concentration and a decrease in specific CO emission There was an increase in engine specific HC and CO and decrease in NOx and PN emission when the EGR was introduced A study [16] showed that the engine power, torque and NOx emissions in n-butanol-gasoline blended fuel depended more on the operating parameters, which directly affected the combustion process It was also found that HC, CO, and CO2 emissions were related to fuel properties Another study [17] on n-butanol-gasoline blended fuels showed that the n-butanol addition to gasoline has improved the combustion As a result, the UHC and CO emissions declined by 26% and 32% than gasoline From this literature review, it can be concluded that the addition of oxygenates had reduced the HC, PN and CO emissions to a significant extent without bringing much change in the performance Despite its benefits, some oxygenates have some limitations such as lower energy density, lower vapour pressure and water miscibility Recently, furan based fuels are emerging because of their advantages over alcohols such as ethanol Furan based fuels are known to have a higher energy density than ethanol and they are non-soluble in water [18] Few experimental results have also revealed their higher octane number and knock resisting tendency which made it an undisputed choice among the alternatives Though there is a book of information available on alcohols and other alter- natives, furan based additives lack some essential research The aim of this study was to investigate the performance, emission and combustion characteristics for 3-different blends of 2Methyl Furan (M10, M20 and M30) and unleaded gasoline at a constant load of 20 N m 2-Methyl Furan is known to have a higher oxygen percentage when compared to conventional fuel like gasoline which ensures a good combustion quality They thus have the potential to reduce emissions such as CO and HC and so this alternative was chosen as the oxygenated additive in this experiment Another experiment was carried out on the same fuel blends with a retardation of 2°CA in the ignition timing to counter the NOx emission and at the same time to investigate the effects of retardation on the performance and combustion characteristics for the same fuel blends Experimental method and apparatus The experiment was carried out in an inline four-cylinder fourstroke water cooled MPFI (Multi Point Fuel Injection) SI engine from a Maruti Zen manufactured by Suzuki The specifications of the engine and the measurement precision are given in Tables and respectively The bore and stroke of the engine are 72 and 61 mm respectively The schematic representation of the engine with the other inter-connected components is shown in Fig The engine is connected with an eddy current dynamometer (TMEC50 by TECHNOMECH) which is used for the purpose of loading An electronic balance (strain gauge measurement) was used for the measurement of fuel-flow and an intake air mass flow sensor was used for quantifying the airflow A PCB water-cooled stand-alone-signal type piezoelectric pres- Table Test engine specifications No Description Specification Make Type Bore Stroke length Compression ratio Displacement Maximum power (@ 6000 rpm) Maximum torque (@ 4500 rpm) Maruti (Zen) Water–cooled MPFI SI Engine 72 mm 61 mm 9.4:1 993 cc 45 kW Table 78.48 N m Measurement precision No Measurement Precision Load (N) Speed (rpm) Time (s) Temperature (°C) Crank angle (°) CO (%) HC (ppm) (propane) NOx (ppm) 25 0.2 0.1 0.01 1 Please cite this article in press as: H Sivasubramanian, Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2-Methyl FuranUnleaded gasoline blends in a MPFI SI engine, Alexandria Eng J (2017), http://dx.doi.org/10.1016/j.aej.2016.12.014 H Sivasubramanian Figure sure transducer (PCB Piezotronics) mounted on the firstcylinder head was used for gauging the in-cylinder pressure An encoder manufactured from India was used for measuring the crank angle Exhaust gases such as HC and CO were measured by a multi-gas analyser (NPM-MGA-1, Netel India Limited) working on principle of NDIR and NOx gas was measured by the same instrument working by the principle of electrochemical method The engine was allowed to run for as long as it was necessary to consume the remaining fuel from the previous experiment For each experiment, the engine was allowed to reach a stable condition and then the measurements were recorded The exhaust gases were measured by inserting an extension pipe in the exhaust pipe The probe of the gas analyser was introduced into the extension pipe and the readings were noted after steady values are obtained in the LCD screen of the analyser The readings were taken for a speed range of 1400–2800 rpm, with an increment of 200 rpm at a constant load of 20 N m Test fuel 2-Methyl Furan is a highly flammable liquid which has a higher octane rating It is a clear fluid which is colourless to yellow to amber in appearance They have ether-like odour and are highly stable under normal temperatures and pressures They are insoluble and they float in water [19] Their high octane rating enables it to be used in engines with higher compression ratios without occurrence of knocking 2-Methyl Furan (MF) is produced by the hydrogenation of furfural, which is the most common method employed for the production of furans [20] The other physical and chemical properties of MF are shown in Table In this experiment, the fuels used were gasoline and MF Unleaded gasoline was obtained from a Test set-up Table Properties of UG and 2-methyl furan [11,19,21] Property 2-Methyl furan UG Chemical formula Molecular weight (g/mol) Density @ 20 °C (kg/m3) O/C ratio H/C ratio Gravimetric oxygen content (%) Auto ignition temperature (°C) Lower heat value (MJ/kg) Latent heat of vaporisation (kJ/kg) Stoichiometric air-fuel ratio Research Octane Number (RON) Motor Octane Number (MON) Initial boiling point (°C) Solubility in water (vol%) Laminar flame speed (cm/s) C5H6O 82.1 913.2 0.2 1.2 19.51 450 31.2 358.4 10.05 103 86 64.7 0.3 70 C2–C14 100–105 744.6 1.795 257 42.9 305 14.46 96.8 85.7 32.8 Negligible 51 local gas station and MF was bought from a local retailer (Lab chemicals, Chennai) Three different concentrations of MF (10%, 20% and 30%) were blended with gasoline during this experiment Results and discussion 4.1 Performance characteristics Brake Thermal Efficiency (BTE) of an engine is the ability of an engine to convert the heat energy of fuel into mechanical power output BTE is one of the key parameters which enlightens the performance of the engine Fig shows the variation of BTE with engine speed for different concentrations of Please cite this article in press as: H Sivasubramanian, Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2-Methyl FuranUnleaded gasoline blends in a MPFI SI engine, Alexandria Eng J (2017), http://dx.doi.org/10.1016/j.aej.2016.12.014 Effect of Ignition Delay (ID) BTE vs Speed @ 20 Nm (With Retardation) BTE vs Speed @ 20 Nm 30 30 UG UG 25 M10 M10 M30 15 M20 20 BTE (%) M20 20 10 M30 15 10 5 1600 1800 2000 2200 2400 2600 2800 Speed (RPM) 1800 2000 2200 2400 2600 2800 Speed (RPM) Brake Thermal Efficiency (BTE) vs speed 4.2 Emission characteristics In this section, the emission of CO, HC and NOx with the addition of MF in gasoline is discussed CO is a colourless, odourless and poisonous gas which is formed mainly by the incomplete combustion of carbon-containing fuels in vehicles CO binds to haemoglobin with about 240 times the affinity of oxygen and reduces the oxygen delivery to the tissues [24] Their immense effects urge the need to mitigate their discharge into the atmosphere The variation of CO with the engine CO vs Speed @ 20 Nm 0.03 UG M10 M20 0.02 M30 0.01 00 00 00 28 26 00 00 00 24 22 20 00 0.00 18 MF (M10, M20 and M30) and unleaded gasoline at a constant load of 20 N m It is evident from the figure that BTE for the blends is higher than UG It was witnessed that the BTE at 1400 rpm is 14.45% for UG and increases by 7.8%, 12.45% and 19.1% for M10, M20 and M30 respectively This trend is because of the higher oxygen content of MF assisting in completeness of combustion Apart from the oxygen enrichment, the higher latent heat of vaporisation of MF increased the amount of heat absorbed by the fuel to vaporise Thus the heat loss from the cylinder was minimised and the intake charge is made colder increasing the volumetric efficiency As a result, the work required to compress the charge decreased resulting in increased BTE [22] In addition to this, the higher laminar flame speed of MF made the mixture turbulent and ensured homogeneity of the mixture [23] BTE was observed to increase with the speed as the fuel supply increased further with speed At a speed of 2800 rpm, the BTE for gasoline is 26.1% and it increased by 5.7%, 7.27% and 11.11% for M10, M20 and M30 respectively Although there was an increase in BTE at higher speeds, the effect of blend decreased as the percentage increase in BTE had reduced at higher operating speeds This was so because, at higher speeds the combustion time was reduced and therefore suppressing the effect of oxygen enrichment of the blend Fig shows the variation of BTE with speed when the ignition was retarded by 2°CA It was found that at retarded condition, BTE had decreased by 3.21%, 4%, 3.5% and 4.62% for UG, M10, M20 and M30 respectively at 1400 rpm when compared to BTE at condition without retardation It was so because as the ignition was retarded, the ability to utilise the maximum heat energy from the fuel decreased and some of the fuel remained unburnt 00 Figure Figure Brake Thermal Efficiency (BTE) vs speed [with retardation] 14 1600 CO (%) 1400 1400 16 BTE (%) 25 Speed (RPM) Figure CO vs speed speed at a constant load of 20 N m is shown in Fig It was noted that the CO emissions were lower for the blends than UG and their levels decrease further with increase in blend percentage At 1400 rpm, it was 0.0285% for UG and decreased by 5.26%, 8.77% and 12.28% respectively for M10, M20 and M30 This was because of the sufficient supply of oxygen by MF leading to complete combustion The air-fuel ratio of MF (10.05) was lesser than UG (14.46) which highlights the occurrence of leaner combustion In lean conditions, the CO emissions were reduced [11] At higher speeds (2800 rpm), it was 0.02% for UG and decreased by 4%, 10%, and 12.5% for M10, M20 and M30 respectively It was evident, that the percentage decrease in CO decreased This is due to the reduced availability of combustion time at higher speeds making the blend addition less effective Fig shows the variation of CO emissions with speed when the ignition was retarded by 2°CA As the spark timing was retarded, the CO emissions had increased when compared to normal operating condition (without retardation) This delayed ignition would affect the efficiency of the combustion process where all fuels might not be completely combusted despite the fact that furan based additives are good oxygen enhancers HC emissions are obtained when the fuel in the engine is partially burned Hydrocarbons react in the presence of sunlight and nitrogen oxides to form ozone, which is a major component of smog It is also known that hydrocarbons have the Please cite this article in press as: H Sivasubramanian, Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2-Methyl FuranUnleaded gasoline blends in a MPFI SI engine, Alexandria Eng J (2017), http://dx.doi.org/10.1016/j.aej.2016.12.014 H Sivasubramanian CO vs Speed @ 20 Nm (With Retardation) HC vs Speed @ 20 Nm (With Retardation) 200 0.04 UG UG M10 M10 150 M30 Figure CO vs speed [with retardation] potential to cause cancer [25] HC emissions give us an idea about the quality of air-fuel mixture and the completeness in combustion The products formed from 100% combustion are H2O and CO2 The incompleteness in combustion results in unburned HCs [28] HC emissions decrease with the addition of MF and decline further with the increase in blend concentration From Fig 6, it is inferred that at 1400 rpm, it is 135 ppm for gasoline and had fallen by 4.44%, 6.6% and 10.37% for M10, M20 and M30 respectively The laminar flame speed of MF is higher which makes mixing of fluids homogeneous The homogeneity of the air-fuel mixture increased with the blend and it burned the unburned hydrocarbon residues that were left struck in the crevices The faster flame speed also eliminates the occurrence of flame quenching at the walls Also the blend achieves oxygen enrichment which improved the quality of combustion At higher speeds (2800 rpm), the HC emission had fallen down significantly This is because of the wide-spread flame of the blend which burned out the unburned hydrocarbons and eliminates the problem associated with partial burning [26] The fuel supply also increased at higher speeds which in turn raised the O2 content At 2800 rpm, it is 88 ppm for gasoline and diminished by 3.4%, 5.68% and 10.22% respectively for M10, M20 and M30 The percentage decrease had fallen because of the reduced combustion duration Fig shows the variation of HC emis- HC vs Speed @ 20 Nm 150 UG M10 M20 HC (ppm) 100 M30 50 Speed (RPM) HC vs speed 00 28 00 26 00 24 00 00 22 00 00 20 18 16 14 00 Figure 00 28 00 26 00 24 00 22 Speed (RPM) Speed (RPM) Figure 20 00 18 14 00 28 00 26 00 24 22 00 20 18 16 14 00 00 0.00 00 50 00 0.01 00 100 00 0.02 M20 16 M30 HC (ppm) M20 00 CO (%) 0.03 HC vs speed [with retardation] sions with speed when the ignition was retarded by 2°CA As the spark timing was retarded, the HC emissions had increased when compared to the HC discharge at normal operating condition (without retardation) It increased by 11.11%, 10.85%, 10.31% and 13.22% for UG, M10, M20 and M30 respectively for a speed of 1400 rpm This was because the flame front does not have the sufficient time to reach all the crevices and burn out the unburned hydrocarbons The formation of NO follows a mechanism called the Zeldovich mechanism, which consists of a series of reactions It is dominated by three reactions: O ỵ N2 ẳ NO ỵ N 1ị N ỵ O2 ẳ NO ỵ O 2ị N ỵ OH ẳ NO ỵ H 3ị The thermal NOx which is produced by the oxidation of nitrogen in the post-flame zone is the major contributor in NO emissions [29] The reaction (1) has higher activation energy because the nitrogen present in the triple bond is difficult to break, which leads to a slower pace of NO formation [30–32] In addition to this, the formation of NO is highly endothermic and this reaction gets activated at a very high temperature (1800 K) at stoichiometric combustion and decreases away from that point The dissociation of O2 results in the formation of free oxygen atoms This reacts with the nitrogen molecules at a higher temperature and results in a simple chain mechanism postulated by Zeldovich [31] In general, for a gasoline powered engine, reaction (2) is activated only at fuel lean combustion, where the supply of oxygen through air is sufficiently high In this case, when the blend percentage increased, it ultimately leads to increased oxygen content This higher oxygen content causes stoichiometric combustion, increasing its in-cylinder temperature, which aids reaction (2) [31] The hydrocarbon radicals present in the fuel react with nitrogen to form amines These amines are then converted into intermediate compounds which, later form NO [33] Fig shows the variation of NOx emission with UG and the blends of MF and UG It is seen from the figure, the emission increased with the blend than that for UG and further elevated with the increase in blend percentage This can be attributed to the higher oxygen content in the MF blended fuels which increased the oxygen to fuel ratio in the Please cite this article in press as: H Sivasubramanian, Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2-Methyl FuranUnleaded gasoline blends in a MPFI SI engine, Alexandria Eng J (2017), http://dx.doi.org/10.1016/j.aej.2016.12.014 Effect of Ignition Delay (ID) NO x vs Speed @ 20 Nm (With Retardation) NOx vs Speed @ 20 Nm 5000 UG M10 M20 3000 M30 2000 1000 M10 4000 NO x (ppm) 4000 M20 M30 3000 2000 1000 00 00 28 00 26 22 24 00 00 20 00 00 18 16 00 00 28 00 00 00 26 24 22 00 20 00 18 00 16 14 00 14 NO x (ppm) 5000 UG Speed (RPM) Speed (RPM) NOx vs speed Figure NOx vs speed [with retardation] Pressure Vs Crank Angle @ 20 Nm 40 UG M10 30 -75 -50 M30 10 25 50 75 CA Pressure vs crank angle Figure 10 Pressure vs Crank Angle @ 20 Nm (With Retardation) 40 UG M10 30 4.3 Combustion characteristics In this section the combustion characteristics that include pressure-crank variation and heat release rate are discussed Fig 10 shows the variation of in-cylinder pressure with crank angle for UG and the blends The peak pressure values were higher for the blends than UG and among the blends, M30 was found to have the highest pressure It was 32.125 bar for M30 and it was followed by M20, M10 and UG that had values of 31.92, 30.82 and 30.745 bar respectively The primary reason for this trend is the higher oxygen content of MF than UG The curve rise was earlier for the blends (9° aTDC) compared to UG (10° aTDC) The higher laminar flame speed of MF reduced the ignition delay allowing the curve to rise earlier [27] When the ignition was retarded, the curve rise was M20 20 -25 Pressure (bar) fuel-rich zones resulting in more complete combustion and thus increasing the in-cylinder temperature [34] Besides, the higher laminar flame speed of MF blended fuels [35] would enhance the flame propagation which in turn burns all the oxygenated fuels resulting in improved combustion quality, rising the in-cylinder temperature [36] At 1400 rpm, it amounted to 787 ppm for UG and increased by 14.99%, 29.22% and 55.65% for M10, M20 and M30 respectively It further went up with the increase in speed as the fuel intake also increased At higher speeds (2800 rpm), it was 3493 ppm for UG and increased by 14.11%, 20.69% and 29.63% for M10, M20 and M30 respectively Also there won’t be much of burned gas fraction from the previous cycle, as it will hinder complete combustion [26] Fig shows the variation of NOx with speed when the ignition was retarded by 2°CA As the spark timing was retarded, the NOx emissions have reduced when compared to the NOx discharge at normal operating condition (without retardation) at lower speeds This was due to the incomplete combustion which reduced the in-cylinder temperature resulting in lower NOx than at normal conditions without any retardation It decreased by 13.97%, 12.15%, 11.5% and 8.16% respectively for UG, M10, M20 and M30 respectively for a speed of 1400 rpm when compared to NOx emissions at normal operating condition (without retardation) The trend seems to increase with speed but it surprisingly decreased at higher speeds (2600 and 2800 rpm) for M20 and M30 These deviations can be attributed to diminished combustion duration at higher speeds which shows that the effect of ignition delay plays a crucial role at higher speeds Pressure (bar) Figure -75 -50 -25 M20 M30 20 10 25 50 75 CA Figure 11 Pressure vs crank angle [with retardation] delayed and the value of peak pressure has become 30.715, 30.79, 31.746 and 32.08 bar respectively which are slightly lower than that at normal conditions as shown in Fig 11 The reason for lower peak-pressure is that the piston starts to move from TDC to BDC which decreased the pressure in the cylinder as the volume increased Fig 12 shows the varia- Please cite this article in press as: H Sivasubramanian, Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2-Methyl FuranUnleaded gasoline blends in a MPFI SI engine, Alexandria Eng J (2017), http://dx.doi.org/10.1016/j.aej.2016.12.014 H Sivasubramanian Heat Release Rate vs Crank Angle @ 20 Nm 60 UG M10 HRR (J/CA) 40 -20 M20 M30 20 -10 10 20 30 40 CA -20 Figure 12 Heat release rate vs crank angle Heat Release Rate vs Crank Angle @ 20 Nm (With Retardation) 60 UG M10 HRR (J/CA) 40 M30 20 -10 10 -20 Figure 13 M20 20 30 40 CA Heat release rate vs crank angle [with retardation] tion of HRR with CA The rate of heat release was higher for MF than for UG It was 51 J/CA for UG and increased by 0.98%, 2.9% and 3.92% for M10, M20 and M30 respectively The higher latent heat of vaporisation of the blends would absorb more heat to vaporise and made the intake charge colder Thus the intake charge density is increased and more amount of MF was injected into the cylinder [27] This rises the O2 percentage involved in the combustion resulting in enhancement of HRR Similar to the pressure curve, the curve rise for HRR was also earlier for the blends than UG which might be attributed to the reduced ignition delay due to its higher flame speed The curve rise occured at 5° aTDC for UG and M10 and 4° aTDC for M20 and M30 In Fig 13, as the ignition timing was retarded, the maximum value of heat release had reduced by 1.33%, 1.59%, 1.61% and 1.69% respectively for UG, M10, M20 and M30 when compared to normal conditions (without retardation) The maximum value of heat release was slightly lowered as the ignition occurs when piston descended down to BDC reducing the heat release value The curve rise was also slightly delayed to 7° aTDC for UG and M10 and 6° aTDC for M20 and M30 Conclusion In this study, the performance, emission and the combustion characteristics are studied for a SI engine fuelled with MF at different concentrations (10%, 20% and 30%) and UG The experiment was carried out at a constant load of 20 N m with speed ranging from 1400 rpm to 2800 rpm with increments of 200 rpm Another experiment with a retardation of 2°CA in ignition timing was carried out under the same operating parameters The following results were obtained through these tests:  The BTE was improved by blending MF with gasoline M30 showed the highest BTE among the tested fuels The BTE was 14.45%, 15.58%, 16.25% and 17.21% respectively for UG, M10, M20 and M30 at 1400 rpm and continued to increase further at higher speeds  CO and HC emissions declined with addition of blends The higher oxygen content and laminar flame speed of MF have reduced CO and HC to a significant extent At lower speed, CO emission was 0.0285%, 0.027%, 0.026% and 0.025% for UG, M10, M20 and M30 respectively and HC emission was 135, 129, 126 and 121 ppm for UG, M10, M20 and M30 respectively At higher speeds, both HC and CO continued to decrease further  The NOx emissions were raised with addition of blends and at lower speed, NOx emissions were lower than those emitted at higher speeds At a speed of 2800 rpm, the fuel intake increased which aided in oxygen enrichment and increased the in-cylinder temperature It was 3493, 3986, 4216 and 4528 ppm for UG, M10, M20 and M30 respectively  The curve rise for in-cylinder pressure and 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characteristics with LPG injection, Int J Energy Environ (2011) 761–770 Please cite this article in press as: H Sivasubramanian, Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2-Methyl FuranUnleaded gasoline blends in a MPFI SI engine, Alexandria Eng J (2017), http://dx.doi.org/10.1016/j.aej.2016.12.014 ... article in press as: H Sivasubramanian, Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2- Methyl FuranUnleaded gasoline blends in a MPFI SI engine, Alexandria... H Sivasubramanian, Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2- Methyl FuranUnleaded gasoline blends in a MPFI SI engine, Alexandria Eng J (20 17),... this article in press as: H Sivasubramanian, Effect of Ignition Delay (ID) on performance, emission and combustion characteristics of 2- Methyl FuranUnleaded gasoline blends in a MPFI SI engine, Alexandria