Unregulated emissions and health risk potential from biodiesel (KB5,KB20) and methanol blend (M5) fuelled transportation diesel engines
Avinash Kumar Agarwal a, *, Pravesh Chandra Shukla b, Chetankumar Patel a,Jai Gopal Gupta a, Nikhil Sharma a, Rajesh Kumar Prasad a, Rashmi A. Agarwal a
a Engine Research Laboratory, Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, Indiab Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India
a r t i c l e i n f o
Article history:Received 25 December 2015Received in revised form5 March 2016Accepted 16 March 2016Available online xxx
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a b s t r a c t
Diesel engine emissions consist of several harmful gaseous species, some of which are regulated bystringent emission norms, while many others are not. These unregulated emission species are respon-sible for adverse environmental impact and serious health hazards upon prolonged exposure. In thisstudy, a four-cylinder, 1.4 l, compression ignition (CI) engine was used for characterization of unregulatedgaseous exhaust emissions measured at 2500 rpm at varying engine loads (0, 25, 50, 75 and 100%). Thetest fuels investigated were Karanja biodiesel blended with diesel (KB5, KB20), methanol blended withdiesel (M5) and baseline mineral diesel. Fourier transform infrared (FTIR) emission analyzer was used tomeasure unregulated emission species and raw exhaust gas emission analyzer was used to measureregulated emission species in exhaust. Results show an increasing trend for some of the unregulatedspecies from blends of biodiesel such as formaldehyde, acetaldehyde, ethanol, n-butane howevermethane reduced upon using these oxygenated fuel blends except methanol, compared to baselinemineral diesel. Nevertheless, no significant changes were observed for sulfur dioxide, iso-butane, n-oc-tane, n-pentane, formic acid, benzene, acetylene and ethylene upon using biodiesel and methanol blends.
Biofuels have emerged as a renewable substitute for conven-tional petroleum based fossil fuels, for both on-road and off-roadvehicles and stationary power generators [1]. Biodiesel and pri-mary alcohols are the most accepted biofuels. Vegetable oilscontain triglycerides, which react with primary alcohols in thepresence of a suitable catalyst such as KOH or NaOH, underappropriate reaction conditions to yield methyl esters and glycerol.This process is known as transesterification. Biodiesel is a diesel likeoxygenated renewable fuel, which has ~11% (w/w) oxygen [1,2]. Onthe other hand, primary alcohols are also oxygenated fuels, whichcan be blended with mineral diesel in lower concentrations. Alco-hols can be produced by fermentation of sugarcane juice and otherrenewable resource such as biomass and waste products, which arereadily available in rural areas. It has been reported in severalstudies that alcohol blends with diesel are superior to mineral
al, et al., Unregulated emissioines, Renewable Energy (201
diesel in terms of higher efficiency and lower emissions [1,3]. Dieselengines can accept up to 20% methanol blended with diesel easilywith either little or no engine hardware modifications [4,5]. One ofthe main concerns related to diesel engines is the emissions ofparticulate matter (PM) and oxides of nitrogen (NOX), with minoremissions of unburnt hydrocarbons (HC) and carbon monoxide(CO). Diesel particulates mainly consist of elemental carbon andorganic carbon (EC/OC) alongwith sulfates and ash. Volatile organiccarbon (VOC) and unburned hydrocarbons (HC) present in thediesel engine exhaust consist of several harmful hydrocarbonspecies. Apart from regulated gaseous emissions, diesel exhaustconsists of a large number of unregulated species as well. Some ofthese unregulated emissions include alkanes, aldehydes, benzene,toluene, xylene (BTX), alcohols and ketones.
Correa and Arbilla, 2008 [6] carried out experiments usingcastor oil derived biodiesel blended (2, 5, 10 and 20% v/v) withdiesel for detecting unregulated emissions and they reportedincreased formaldehyde (2.6%, 7.3%, 17.6%, 35.5%) and acetaldehyde(1.4%, 2.5%, 5.4%, 15.8%) emissions from biodiesel blends comparedto baseline diesel. However, Peng et al., 2008 [7] reported 23%reduction in formaldehyde emissions for 20% (v/v) waste cooking
ns and health risk potential from biodiesel (KB5, KB20) andmethanol6), http://dx.doi.org/10.1016/j.renene.2016.03.058
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oil biodiesel blend. Karavalakis et al., 2009 [8] investigated unreg-ulated emissions in Athens driving cycle (ADC) and new Europeandriving cycle (NEDC) using rapeseed and palm biodiesel blends (5,10 and 20% v/v) fuelled engine. They observed increased formal-dehyde emissions from both biodiesel's blends, while palm bio-diesel blend resulted in reduced aldehyde emissions. Di et al., 2009[9] investigated various unregulated emissions from a diesel enginefuelled by waste cooking oil biodiesel blends vis-�a-vis baselinemineral diesel. They reported that formaldehyde, 1,3-butadiene,toluene and xylene emissions decreased whereas acetaldehyde andbenzene emissions increased with increasing biodiesel blending.He et al., 2009 [10] reported that formaldehyde emission contri-bution was 46.2% and 62.7% in carbonyl emissions from soybeanbased biodiesel and diesel respectively in a diesel engine experi-ment. They also observed significant amount of acetaldehyde,acrolein, and acetone among unregulated emissions. Karavalakiset al., 2009 [11] measured unregulated emissions in ADC & NEDCdriving cycles from soy based biodiesel blends (5, 10 and 20% v/v)vis-�a-vis mineral diesel. They reported that carbonyl emissionswere relatively lower from biodiesel blends. In another study, it wasreported that carbonyl emissions were not affected by lower bio-diesel blends [12]. Magara-Gomez et al., 2012 [13] comparedemissions from soybean biodiesel blends (B50, B100) and beeftallow biodiesel blends (BT50, BT100) with baseline mineral diesel.They reported significant reduction in unregulated emissions suchas toluene, ethylbenzene and xylene emissions. 23, 42 and 40%reduction in formaldehyde emissions were observed from B50,B100 and BT100 respectively vis-�a-vis mineral diesel.
Some studies [14e17] also reported unregulated emissions fromalcohol blends fuelled diesel engines. Chao et al., 2000 [14] inves-tigated methanol containing additives blended diesel (0, 5, 8, 10and 15% v/v) in a heavy-duty diesel engine. They observed rela-tively higher carbonyl emissions and other unregulated emissionssuch as acrolein, benzaldehyde. Cheung et al., 2009 [4] also re-ported higher emissions of acetaldehyde, formaldehyde andmethanol emissions from biodiesel-methanol blends (BM5, BM10and BM15) compared to baseline diesel. They reported that 1,3-butadiene and benzene emissions were relatively lower frombiodiesel-methanol blends, while toluene and xylene were similarto that of mineral diesel. Zhang et al., 2010 [18] found decreasingtrend of ethyne, ethylene and 1,3-butadiene emissions uponapplying diesel/methanol (10, 20 and 30% fumigation methanol)‘compound combustion scheme’ on a four-cylinder diesel engine.They reported higher emissions of benzene, toluene, xylene, un-burned methanol and formaldehyde with increasing methanolconcentration in the test fuel. Table 1 shows the health effects ofvarious unregulated emissions from diesel engines, which arefuelled by mineral diesel, biodiesel and diesel-alcohol blends. Thistable helps one understand the associated health and environ-mental costs of using different fuels, including renewable fuels.
In the present study, various unregulated emissions weremeasured in the exhaust from a CI engine, which was fuelled byKaranja biodiesel blended with diesel (KB5, KB20), methanolblended with diesel (M5), and baseline mineral diesel. This studybrings out some important inferences in terms of unregulatedemissions emitted by the alternative fuelled engines in real-time. Itis also well known that various unregulated organic compoundspresent in the engine exhaust undergo secondary chemical re-actions in the environment and form secondary and tertiary pol-lutants. Real-time measurement of exhaust provides informationabout the primary organics and hydrocarbons emitted by the en-gine. No study has been performed so far on the real-time mea-surements of unregulated emissions for these alternative fuels.
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2. Experimental setup and methodology
A four cylinder, water-cooled, naturally aspirated, trans-portation diesel engine was used in this experimental study. Testengine produces rated torque of 85 Nm at 2500 rpm engine speed.Technical specifications of the engine are given in Table 2. The fuelinjection system consists of a rotary fuel injection pump and sole-noid injectors. Fig. 1 shows the schematic of the experimentalsetup.
Experiments were performed on a diesel engine, which wasfuelled by mineral diesel, biodiesel blends (KB5, KB20) and meth-anol blended (M5) with diesel. Emissions were measured forregulated and unregulated species using a raw exhaust gas emis-sion analyzer (Horiba; EXSA 1500) and a Fourier transform infrared(FTIR) emission analyzer (Horiba; MEXA 6000FT-E) respectively.FTIR spectrometry was used for obtaining infrared absorptionspectrum of high resolution by a combination of an interferometerand high-speed Fourier transform. CO and CO2 were measured byusing non-dispersive infrared (NDIR) measurement principle. Totalhydrocarbons (THC) were measured by flame ionization detection(FID) analyzer and NOX was measured by Chemiluminescense(CLD) analyzer. Both emission analyzers were equipped with aheated exhaust gas sampling system, which was maintained at191 �C as per the norms of US Environmental Protection Agency(USEPA) in order to avoid condensation of moisture and highboiling point hydrocarbons during sampling. Detailed specifica-tions of the regulated and unregulated emission measurement in-struments are given in our previous paper [40].
Before sampling the exhaust, engine was operated for 10 min atevery engine operating condition, in order to obtain thermallystable condition of the engine. After achieving the thermal steadystate, exhaust gas samples were drawn simultaneously for regu-lated and unregulated gaseous species measurement. Exhaustsamples were drawn at five engine loads (0, 25, 50, 75 and 100%) atthe rated torque speed of 2500 rpm. Each data point represents anaverage of 60 consecutive measurements and standard deviation isshown in the plots.
3. Results and discussion
The main concern remains in diesel engines is the dilemma ofPM and NOx trade-off. There are several hydrocarbon species pre-sent in the diesel engine exhaust, which are carcinogenic andmutagenic in nature and lead to serious problems in human bodyupon prolonged exposure. These hydrocarbon species condense onthe condensate sites (generally nano-particles) present in the en-gine exhaust and form very harmful aerosols, when they arereleased into the environment via the engine tail-pipe. Therefore, itis necessary to characterize various emission species from dieselengines, especially when they are being used with alternative fuelssuch as biodiesel and primary alcohols and compare their potentialtoxicity with baseline mineral diesel. In this section, experimentalresults are discussed in two separate sections namely regulatedemissions and unregulated emissions.
3.1. Regulated gaseous emissions
Emissions of CO, HC, NOX (NO, N2O and NO2), which comprisesof nitric oxide (NO), nitrogen dioxide (NO2), nitrous oxide (N2O) inthe exhaust have been compared and discussed in this section forthe test fuels used in this study.
3.1.1. Carbon monoxide (CO) and unburnt hydrocarbon emissions(HC)
All the blended fuels resulted in slightly higher CO emission
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Table 1Health and environmental effects of unregulated emission species [19e39].
Unregulated emission species Possible health and environmental effect
Methane(CH4)
� GHG with greenhouse index 21 times that of CO2.
� Simple asphyxiant, when inhaled.� Leads to headache, dizziness, weakness, nausea, vomiting, and loss of consciousness.
n-butane(n-C4H10)
� Inhalation causes euphoria, drowsiness, narcosis, asphyxia, cardiac arrhythmia, and fluctuations in blood pressure.
Iso-butane(iso-C4H10)
� Simple asphyxiant, when inhaled.� Causes fatigue, dizziness, headache, and nervous system damage.
Normal pentane(n-C5H12)
� Affects central nervous system.� Causes erythema, hyperaemia, swelling, pigmentation, and anoxia.� Burning sensation accompanied by itching, and blisters.
Normal octane(n-C8H18)
� Giddiness, vertigo, skin redness and rashes, brain irritation or apnoeic anoxia.� Causes throat and lungs problems, and headache.
Ethylene(C2H4)
� Causes headache, drowsiness, dizziness, nausea, weakness and unconsciousness.� Causes irritation to respiratory system, alters carbohydrate metabolism.� Acts as ozone formation agent.
Acetylene(C2H2)
� Causes suffocation, dizziness, headache, unconsciousness, and nausea.� Inhalation results in high blood pressure, fits and abnormal heart rhythms.
Benzene(C6H6)
� Drowsiness, dizziness, rapid or irregular heart-beats, headaches, tremors, confusion, unconsciousness, and carcinogenic to humans.� Chromosomal aberrations in human peripheral lymphocytes.
Formaldehyde(HCHO)
� Irritation in eyes, nose, and throat, coughing, and skin irritation.� Considered as human carcinogen, asthma-like respiratory problems.� Affects pregnancy and reproductive system.
Acetaldehyde(CH3CHO)
� Irritation of skin, eyes, mucous membrane, throat, respiratory tract, nausea, vomiting and headache.� Probable carcinogen.
Formic acid(HCOOH)
� Causes teary eyes, running nose, coughing, sore throat, bronchitis, shortness of breath, pulmonary edema, liver and kidney damage.� Burns tissue and membrane of the skin, and respiratory tract.
Ethanol(C2H5OH)
� Causes unconsciousness.� Affects formation of anti-diuretic hormones, leading to brain disability.� Affects nervous system of developing embryo and foetus.
Sulphur dioxide(SO2)
� Higher concentration (>100 ppm) causes danger to life and health.� Burning sensation in nose and throat, breathing difficulties, and severe airway obstructions.
Table 2Technical specifications of the test engine.
Particulars Specifications
Make/Model Tata/Indica 1.4 LNumber of cylinders 4, InlineBore/Stroke 75 mm/79.5 mmFuel injection pump Rotary fuel injection pumpCapacity 1405 ccRated power 53.5 PS @ 5000 rpmRated torque 85 Nm @ 2500 rpmCompression ratio 22:1Firing order 1-3-4-2
Fig. 1. Schematic of the experimental setup.
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compared to baseline mineral diesel at lower loads (Fig. 2a). Whileno significant difference was observed for CO emission at higherloads amongst all test fuels. At 75% and 100% loads, M5 resulted in
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slightly higher CO emission compared to other fuels. In general, COemission decreased towards intermediate loads and then increasedto reach maxima at full load for all test fuels. KB20 has moderatelyhigher CO emission at lower loads compared to baseline mineraldiesel. KB20 has slightly higher viscosity, which results in largersize distribution of fuel spray droplets, relatively more inefficientfuel-air mixing and higher degree of incomplete combustion atlower loads, which leads to slightly higher CO emission. At 75 and100% loads, higher in-cylinder temperature promoted higherevaporation of biodiesel spray droplets. This helped in achievingrelatively higher degree of complete combustion, which reduced
CO emission from KB20 vis-�a-vis mineral diesel. In addition,inherent fuel oxygen [2] of biodiesel also helped in CO reduction.CO2 emission increased with increasing engine load (Fig. 2b) and its
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Fig. 2. Carbon monoxide (CO), Carbon dioxide (CO2) and unburnt hydrocarbons (HC)in the exhaust.
Fig. 3. Oxides of nitrogen in the exhaust.
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concentration varied from 3.5% to 11% from no load to full load. Alltest fuels showed similar trend for CO2 emission, which indicatedno loss in engine performance for alternate test fuels used in thisstudy.
Fig. 2c shows that mineral diesel emitted lower HC at lowerloads, while blends of biodiesel and M5 emitted higher HC emis-sions. At higher loads, mineral diesel emitted relatively higher HCemissions compared to other test fuels [41]. Lower evaporation ofbiodiesel at lower loads resulted in slightly higher HC emissionsfrom biodiesel blends. Again, increased in-cylinder temperature athigher loads and fuel oxygen content of biodiesel led to reduction inHC emissions. Similarly, use of M5 also led to lower HC emissionsdue to inherent oxygen content of methanol. Fig. 2d shows themoisture (H2O) content in the engine exhaust for all test fuels. H2Ois a by-product of combustion. All test fuels showed same trend ofmoisture content in the exhaust. It is desirable to have highestpossible concentration of moisture and CO2 for higher thermal ef-ficiency and lower emissions, for a given engine power output.
3.1.2. Oxides of nitrogenFig. 3 shows NO, NO2, and N2O emissions measured by FTIR
analyzer (Fig. 3aec) and total NOX emissions measured by Chem-iluminescense analyzer (Fig. 3d) for all test fuels. NO emissionincreased as the engine load increased and reached maxima at fullload for all test fuels (Fig. 3a). NO formation in the combustionchamber is a temperature dependent phenomenon. Since the peakin-cylinder temperature increased with increasing engine load, NOformation also increased [42,43]. NO2 emissionwas higher at lowerengine loads (Fig. 3b). Engine emitted ~50 ppm NO2 at no load,when fuelled by mineral diesel, which becomes negligible at full
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load. Other test fuels showed slightly lower NO2 emissioncompared to mineral diesel. NO2 concentration reduced withincreasing engine load, suggesting that NO2 emission reduced asthe peak in-cylinder temperature increased. NO2 is a paramagneticcompound and is also a key component participating in secondaryaerosol formation. NO2 plays a major role in formation of groundlevel ozone (smog) [44], therefore, it is desirable to have lower NO2emissions in the engine exhaust. Fig. 3c shows the N2O emission,which remains almost negligible for all loads for all test fuels. N2O isa strong greenhouse gas and has global warming potential ~310times that of CO2 (EPA, 2010). Fig. 3d shows NOx emissions, whichwere almost similar to NO emission trend for all test fuels. At higherengine loads, NOx emissions were moderately lower for biodieselblends compared to M5 and baseline mineral diesel. Raheman andPhadatare, 2004 [45] also reported ~26% lower NOx emissions fromKaranja biodiesel and blends compared to baseline mineral diesel.
3.2. Unregulated emissions
Emissions of various unregulated species in the exhaust havebeen compared and discussed in this section for all the test fuelsused in this study. For convenience, they are segregated in differentcategories.
3.2.1. Saturated hydrocarbon compoundsTraces of several saturated hydrocarbons such asmethane (CH4),
n-butane (n-C4H10), n-pentane (n-C5H12) and n-octane (n-C8H18)were emitted in the engine exhaust and weremeasured by the FTIRemission analyzer. Fig. 4a shows that the concentrations ofmethane were negligible at lower engine loads but they were sig-nificant at 75% and 100% engine loads for all test fuels. For 100%
ns and health risk potential from biodiesel (KB5, KB20) andmethanol6), http://dx.doi.org/10.1016/j.renene.2016.03.058
Fig. 4. Saturated hydrocarbon emissions in the exhaust.
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load, methane concentration in the exhaust was in the range of15e30 ppm, depending on the test fuel used. Methane is a stronggreenhouse gas and its greenhouse index is 21 times that of CO2. Itsemission is highest for M5, followed by mineral diesel, KB5 andKB20 at full load. It has been reported that methane can be pro-duced by thermal cracking of longer chain-length hydrocarbons.The increasing concentration of methane at higher engine loadmight be due to methane formation at higher in-cylinder temper-atures [46].
n-butane emission was ~40 ppm (Fig. 4b) at no load for all testfuels except mineral diesel, which was ~25 ppm. As the engine loadincreased, concentration of n-butane decreased and at full load, itwas 5e10 ppm for all test fuels. Biodiesel blends emitted slightlyhigher n-butane compared to mineral diesel. Possibly, mineraldiesel consists of longer chain hydrocarbons (C16), which weremore prone to fragmenting into smaller species (such as n-butane)in presence of biodiesel, possibly due to its molecular oxygen. iso-butane was also observed in very low concentration for all testfuels, which decreased with increasing engine load (Fig. 4c).However n-pentane concentration in the engine exhaust increasedwith increasing engine load (Fig. 4d). At lower loads, n-pentaneemission was relatively higher for M5 compared to other test fuels.n-octane emission (Fig. 4e) was maximum (~10 ppm) at no load for
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all test fuels, which reduced to approximately 2 ppm at full load.The reduction in n-octane occurred due to superior oxidation athigher temperatures at high engine loads.
3.2.2. Unsaturated hydrocarbonsFig. 5 shows the emission of acetylene (C2H2) and ethylene
(C2H4) from all test fuels. Acetylene emission increased at higherengine loads (Fig. 5a). In the engine exhaust, acetylene acts as aprecursor for the formation of pyrolyzed compounds and aromaticcompounds. Therefore, it is desirable to have lower emission ofacetylene. Emission of ethylene was in the range of 5e10 ppm at noload (Fig. 5b), which decreased towards the intermediate load andagain slightly increased at full load.
3.2.3. Aldehydes and alcoholsKB5 and KB20 showed slightly higher formaldehyde (HCHO)
emissions at lower engine loads compared to mineral diesel(Fig. 6a). In general, HCHO emission was higher at lower loads andreduced with increasing engine load for all test fuels. HCHO is aproduct of partial combustion of fuel and lubricating oil in thecombustion chamber. At lower engine load, in-cylinder tempera-ture is relatively lower, which leads to lower evaporation of fuel andhigher degree of incomplete combustion of fuel droplets. As theengine load increased, higher in-cylinder temperature promotedoxidation of formaldehyde (Fig. 6a), resulting in reduction in itsconcentration with increased engine load. For KB20, formaldehydeemission was ~23 ppm at no load, which reduced to ~6 ppm at fullload. Acetaldehyde is the main organic species responsible for theformation of secondary organic aerosols (SOA).
In this study, Acetaldehyde was in the range of ~15e28 ppm atno load (Fig. 6b), which reduced to ~4 ppm at full load. Overallacetaldehyde emission was higher at no load and reduced forhigher loads, similar to the results reported by He et al., 2003 [47]. Itseems that formation of aldehydes is also temperature dependent,which reduces with increased temperature. KB20 showed slightlyhigher acetaldehyde emission for all operating conditions.
Methanol emission was not detected for all test fuels, even fromM5. Ethanol emission showed detectable quantity (~10 ppm) atlower loads however it reduced to 0e2 ppm at full loads for all testfuels (Fig. 6c). Ethanol emission at lower engine loads indicated thatethanol formed during combustion, which re-burnt at higher en-gine loads. Cheung et al., 2008 [15] gave the same reasoning forreduction in ethanol traces at elevated combustion chamber tem-perature. As far as test fuels are concerned, there were no
Fig. 5. Unsaturated hydrocarbon emissions in the exhaust.
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Fig. 6. Aldehydes and alcohols emissions in the exhaust.
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significant differences at similar operating conditions.
3.2.4. Sulfur dioxide (SO2), formic acid (HCOOH) and benzene(C6H6)
Sulfur dioxide (SO2) emission was less than 5 ppm for all testfuels at all operating conditions (Fig. 7a). Sulfur is present in diesel,which forms SO2 after combustion. SO2 promotes formation ofsulfur trioxide (SO3), which eventually gets converted to sulfuric
Fig. 7. Emission of sulfur dioxide (SO2), formic acid (HCOOH) and benzene (C6H6) inthe exhaust.
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acid (H2SO4) in presence of moisture. The presence of sulfuric acidin the exhaust acts as an ingredient for condensation of volatilematerials [48], which promotes particulate formation havinghigher organic carbon content. Therefore, it is desirable to havelower SO2 emission in the engine exhaust. Presence of sulfur in thefuel is also responsible for poisoning of the catalyst present in theafter-treatment devices [48].
Fig. 7b shows that traces of formic acid were ~2 ppm. Benzeneemission was also found to be in quite low concentration, up to~4 ppm (Fig. 7c). Bermudez et al., 2011 [46] reported that aromaticspecies like benzene form due to pyrolysis at higher temperatureand pressure conditions of the combustion chamber. Pyrolysishappens because of insufficient oxygen availability, which helps inpartially oxidizing fuel carbon into several unburnt hydrocarbonproducts, including benzene. Benzene is a known carcinogeniccompound and its emission is undesirable.
Apart from the above discussed emission species, ethane (C2H6),propylene (C3H6), propane (C3H8), 1,3-butadiene (1,3-C4H6),isobutylene (iso-C4H8), iso-pentane (iso-C5H12), acetic acid(CH3COOH), toluene (C7H8), ammonia (NH3) were also measured.These results are not reported individually, however they areshown in section 3.2.5.
3.2.5. Other unburnt hydrocarbonsEmission norms regulate the hydrocarbon emissions from the
vehicles. However it is also important to evaluate the fraction of aparticular hydrocarbon species in HC. Higher concentration of aparticular hydrocarbon species can cause higher toxicity of the HC,depending on their toxic potential. Fig. 8 shows the fraction of in-dividual unregulated species measured in this study. It wasobserved that the emissions of certain hydrocarbon species were inhigher fraction in HC such as formaldehyde, n-butane, acetalde-hyde etc. particularly at lower loads. Fraction of most of thedetected species reduced in HC with increasing engine loads exceptmethane, n-pentane and acetylene. However fraction of unidenti-fied species increased drastically at higher engine loads. This in-dicates that combustion leads to formation of few higher molecularweight species in significant quantity from all test fuels. Operatingconditions near 50%e75% loads resulted in lowest HC concentra-tions (except diesel at 75% load). For mineral diesel, fraction ofunidentified compounds was observed to be significantly highercompared to other test fuels at higher engine loads. This showedsuperiority of alternate fuels over the mineral diesel for reductionin emission of compounds with higher molecular weight. It wasobserved that n-butane contributed a significant fraction in hy-drocarbons at lower and intermediate engine loads from mineraldiesel. Formaldehyde and acetaldehyde emissions were seen insignificant concentrations for all test fuel at lower engine loads,which reduced with increasing load.
The concentration of unidentified hydrocarbon compoundsfrom M5 was significantly higher at lower engine loads. One pointshould be noted that M5 emitted highest traces of methanecompared to other test fuels. The presence of methyl group inmethanol leads to higher emission of methane from M5.
4. Conclusions
Experimental investigation were conducted for finding outseveral unregulated emission species such as nitrous oxide, form-aldehyde, acetaldehyde, formic acid, n-butane, n-pentane,methane, acetylene etc. Important conclusions made from theexperimental results are:
1. All test fuels lead to increase in CO emission at higher engineloads. Higher fuel quantity injected at higher engine load
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Fig. 8. Fraction of unregulated emissions in HC in the exhaust.
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resulted in higher degree of incomplete combustion. HC emis-sions were observed to be higher from alternative fuels used inthis study at lower engine loads. However these alternative fuelsresulted in reduction in HC emissions at higher engine loads.This depicted that alternative fuels are superior for higher en-gine outputs, especially for HC emissions. NOx emissions wereobserved to be marginally lower from alternative test fuels.
2. Hydrocarbon emissions are regulated by the emission regula-tory bodies. These hydrocarbons are mixtures of severaldifferent organic species. Each organic species has differenttoxicity behavior, depending on its toxic potential. Therefore it isimportant to evaluate the emission of most harmful individualorganic species. In this study, some detected hydrocarbons suchas methane, n-pentane and acetylene were observed to be inhigher trace concentrations at increasing loads. On the otherhand, trace concentrations of n-butane, formaldehyde, acetal-dehyde, and ethanol decreased with increasing engine load. Nodefinite trend was observed for ethylene, sulfur dioxide, formicacid, benzene, iso-butane and n-octane emissions.
3. Biodiesel blends emitted lower trace concentrations of methanewhile M5 emitted higher trace concentration of methane vis-a-
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vis baseline mineral diesel. Methane has significantly higherGHG potential therefore biodiesel is a superior fuel for dieselengine. Aldehyde is also a major carcinogenic compound, andbiodiesel blends emitted higher trace concentration. Thereforebiodiesel is advantageous from the point of view of emission ofsome species however it has disadvantage of higher traceemissions of some other organic species.
4. Detected organic species were compared among total hydro-carbons, which indicated that the fraction as well as absoluteconcentration of detected hydrocarbon species reduced signifi-cantly at higher engine loads. Apart from this, the fraction ofunidentified hydrocarbons increased drastically at full load forall test fuels, which subsequently lead to increased HC emissionsat higher engine loads. Higher emissions of unidentified hy-drocarbon species indicate formation of higher molecularweight organic species at higher engine loads.
Overall, this study gave an insight into unregulated emissionsfrom blends of alternative fuels (KB5, KB20 and M5). Though thespecies evaluated in this study are not regulated by the emissionregulations worldwide, they certainly cause several harmful effects,
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depending on their toxic properties. It is also emphasized in thisstudy that even minor concentrations of some species may be moreharmful compared to some of the regulated species, which areemitted in higher concentrations. This study is helpful in drawing alandscape of unregulated species from different alternate fuels andconventional fuels.
Acknowledgements
Authors would like to acknowledge Mr. Roshan Lal of EngineResearch Laboratory, IIT Kanpur for his valuable help in conductingthe experiments.
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