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SAE TECHNICALPAPER SERIES 2000-01-0691

A Comparative Analysis of Combustion Processin D. I. Diesel Engine Fueled with Biodiesel

and Diesel Fuel

A. Senatore and M. Cardone

Universit Federico I

V. RoccoUniversit di Roma Tor Vergata

M. V. PratIstituto Motori CNR

SAE 2000 World CongressDetroit, MichiganMarch 69, 2000


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2000-01-0691

A Comparative Analysis of Combustion Process in D.I. Diesel

Engine Fueled with Biodiesel and Diesel Fuel

A. Senatore and M. CardoneUniversit Federico I

V. RoccoUniversit di Roma Tor Vergata

M. V. PratIstituto Motori CNR

Copyright 2000 Society of Automotive Engineers, Inc.

ABSTRACT

The 1997 Kyoto International Conference Protocolcommitted industrialized countries to reduce their globalemissions of greenhouse gases within the period 2008-2012 by at least 5% with respect to 1990. In view of thisand following the European Community directives, theItalian government approved a three-year pilot project topromote the experimental employment of biodiesel.

The methyl esters of vegetable oils, known as biodieselare receiving increasing interest because of their lowenvironmental impact and their potential as an alternativefuel for diesel engines as they would not require anysignificant modification of existing engines.Consequently, an experimental research program hasbeen developed to evaluate performance and emissionsof a Diesel engine fueled with a methyl ester derived fromrape seed (Rapeseed Methyl Ester or RME) by changingthe composition of the diesel fuel-RME mixture.

This program aims to analyze the performance andemissions of a turbocharged D.I. Diesel engine fueledwith a mixture of RME and diesel fuel. In particular, theexperimental investigation has performed a carefulanalysis of heat release, which has made it possible togive more precise information about the combustion

process.

INTRODUCTION

The conferences of Rio de Janeiro 1992, Berlin 1995,Geneva 1996 and Kyoto 1997, subsequently ratified bythe conference of Buenos Aires in 1998, have resulted inthe promulgation of directives aiming to reduce the globalemission of greenhouse gases by 5% compared to the1990 levels.

In order to reach these goals without restricting theeconomic growth of the individual countries concerned, it

will be necessary to follow some fundamental guide linesincluding:

improvement of production processes;

increased efficiency;

use of alternative energy sources.

In view of these considerations and the EU directives, thegoal of reaching a 7% reduction by the year 2010 wilrequire Italy to reduce global emissions of greenhousegases from about 604 CO2 equivalent Mt/year envisagedfor 2010 to 498 equivalent Mt/year. Specifically, the 106equivalent Mt/year to be eliminated include: 82 Mt o

CO2, 20 equivalent Mt of methane and 4 equivalent Mt ofother greenhouse gases [1].

In particular, the actions needed to achieve theseobjectives can be subdivided into two categories [1]:

A preliminary series of measures will enable Italy tocut its emissions by 75 equivalent Mt/year so that by theyear 2010 these will be below the 1990 values (-2%)These measures, besides suggesting a greater use ofcombined-cycle and co-generation power plants, includethe development and diffusion of high-efficiency internacombustion engines and the modernization of the publictransport system. A modest though significan

contribution (1.5 Mt/year) should also come from thepromotion of biofuels. This is the framework surroundingthe implementation of a three-year pilot project approvedby special legislation on 22 May 1998 [2] which aims topromote the experimental use and facilitate thetechnological development of the product known asbiodiesel, obtained from the esterification of vegetableoils and their derivatives. These preliminary operationswill be supplemented by the further introduction omethane fuel in the transport, industrial, residential andtertiary sectors and the promotion and introduction ofequipment and systems for reducing electricityconsumption in the residential and tertiary sectors.


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Additional measures will ensure that the 7% figurerecommended by the European Union will be reached byenabling a further reduction of 31 equivalent Mt/year.

In the context of the above mentioned pilot project theItalian government has confirmed tax exemptions for anannual total of 125,000 tons of biodiesel. At the end ofthe three year experiment a joint committee will examinethe results obtained in order to assess the possibility ofextending the duration of the project.

These considerations have led to a renewed interest inthe experimentation of biofuels and, in particular, inmethyl esters derived from the transesterification ofvegetable oils.

The research effort in this specific sector includes thecontribution of the team comprising researchers fromDIME and Istituto Motori of Naples and DIM of Rome TorVergata University. These researchers are studying theeffects of different mixtures of biodiesel (in this case rapeseed methyl ester, hereafter referred to as RME) anddiesel fuel on the performance and emissions of differenttypes of engines.

The results obtained so far [3,4,5] show that the biofuelhas good overall behavior, with performance andemission levels comparable to diesel fuel. We havetherefore been encouraged to investigate the combustionprocess of methyl esters more thoroughly. The mostsignificant result obtained in this experimentalinvestigations is the higher emission of nitrogen oxides,which can only be explained after obtaining a thoroughunderstanding of the phenomena characterizing thecombustion process.

EXPERIMENTAL SET-UP

The experimental set-up is comprises a 1929 cc DIturbocharged Diesel engine equipped with an intercoolerand EGR, whose main design characteristics arespecified in Table 1, and an electric brake (Schenk WS260). All engine control signals are interfaced to an AVLPuma V2 Test Commander. The measurements include:

Torque

Speed

Air flow rate (AVL Pintsch Bamag DZK 03)

Fuel flow rate (AVL 7030 - A05)

Relative humidity Temperature

Pressure

Emissions (NO - NO2 NOX - CO - CO2 - O2 - HC)

Smoke (Smokemeter AVL 4010- A01)

Using a fast data acquisition system (Analog Device RTI860 NI DAQ) and an AVL Encoder for trigger and clock,the following signals were acquired:

Instantaneous pressure in two cylinders(AVL GM 12G-90)

Instantaneous fuel injection pressure(AVL 41DP 1200K)

Instantaneous pressure in the intake pipe(AVL 16QP 100c)

Instantaneous pressure in the intake manifold(AVL 16QP 100c)

Instantaneous pressure in the exhaust manifold(AVL 16QP 100c)

Needle lift ( Wolff Hall-Effect trasducer)

FUEL CHARACTERISTICS

ASTM has defined biodieselas the mono alkyl esters olong-chain fatty acids derived from renewable fats suchas oils and animal fats, for use in Diesel engines [6, 7]The definition of mono alkyl esters means that purevegetable oils and mono- and di-glycerides cannot beconsidered as biodiesel. Furthermore, the fact thabiodiesel must be produced from renewable fats

eliminates any confusion with other substances to whichthis name has been attributed in the past. The furtherspecification regarding its general use in Diesel enginesdifferentiates it from other biofuels, such as ethanol oother gasoline substitutes.

The biodiesel used in the experimental tests described inthis paper is a methyl ester of rape seed oil (RME), bothin its pure state and blended with a commercial referencediesel fuel containing less than 500 ppm of sulfur. Themethyl ester is obtained through a transesterificationprocess in which the use of methyl alcohol and thepresence of a catalyst (such as sodium hydroxide opotassium hydroxide) chemically breaks down the oimolecule into methyl esters of the oil and a glycerine byproduct (Fig. 1).

The properties of the two pure fuels are reported in Tab2. The biodiesel can be completely blended with thediesel fuel, does not contain aromatics or sulfur andcontains about 11% by weight of oxygen. The biodiesehas a high cetane number due to the long linear chain othe fatty acid part of the ester. A particularly interestingfeature of both the diesel fuel and the RME is theirthermal and oxidative stability.

Table 1. Engine main characteristics

Displacement 1929 cm3

Compression ratio 19.80.8:1

Bore x stroke 82.6 x 90 mm

Max power 68 kW (92CV) at 4200 rpm

Max torque 19.6 daNm (20.4 kgm) at 2000 rpm

Alimentation With turbocharged Garrett TD 2502

Injection Direct

Fuel injection pump Bosch VER 493 rotary type


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Recent enhancements in the Diesel engine, with thehigher temperatures and pressures involved, and theneed for refineries to remove aromatics and sulfur hasled to an increased interest in the stability of diesel fuel.

Figure 1. Transesterification

Current legislation on diesel fuel does not includespecifications regarding its stability. In order to assessthe thermal stability of RME, European countries use theiodine number which is a measure of the dual bonds inthe fatty acid portion of biodiesel, but this assessment isnot acknowledged in the USA.

In addition to the pure diesel fuel and pure biodiesel,blends of the two fuels were also tested. These had thefollowing compositions, expressed in volumetricpercentage:

Blend A - 30% biodiesel 70% diesel fuel

Blend B - 50% biodiesel 50% diesel fuel

Blend C - 75% biodiesel 25% diesel fuel

We evaluated the density and viscosity of the two purefuels and the three blends (A, B and C) and simulatedtheir distillation behavior. The latter was achieved through

thermogravimetric analysis in both an inert and anoxidative environment by heating the various samplesfrom ambient temperature to 650 C at 10C/min.

As far as density is concerned, we recorded a linearincrease as the percentage of RME in the blendincreased. Viscosity likewise showed an increasing buless marked trend as the RME content increased. Asexpected, substantial differences were observed in thedistillation behavior. While the diesel fuel is composed of

hundreds of compounds which have different boilingpoints, biodiesel contains only a few compounds, mainlyalkyl esters C16-C18, which have boiling points veryclose to the same temperature (330-350C)Consequently, RME does not have a distillation curveproper.

A major experimental campaign conducted in France [8revealed that the addition of 5% of RME to diesel fuedoes not significantly modify the diesel fuecharacteristics or the engines performance in light- orheavy-duty vehicles.

ANALYSIS OF PERFORMANCE AND EMISSIONS

PERFORMANCE Figures 2-4 show the experimentaresults on the performance of the engine fueled with purediesel fuel and pure biodiesel, whose characteristics arespecified in Tab. 2. The present paper examines only theworking conditions for pure fuels and refers readers tothe literature [3, 4, 5] for an analysis of the intermediateblends. It should be remembered that although engineperformance depends directly on the air/fuel ratio, whiletaking into account the different stoichiometric ratio ofbiodiesel (12.6) compared to that of diesel fuel (14.6), thevarious operating conditions must be compared

according to the relative equivalence ratio = /st Fothis reason, and because of the different fuel densitiesthe stoichiometric ratio of each blend has to bedetermined as a weighted mean value according to thecomposition of the blend.

In view of this and for the different lower heating values(see Tab. 2), the comparison between the two fuels andtheir blends must be made in terms of their relativeheating value, which is defined as:

According to this relation we can see that, as thestoichiometric ratios and the heating values compensatefor each other, the diesel fuel and the methyl ester arecharacterized by essentially equivalent relative heatingvalues of around 2,900 kJ/kg. In order to take intoaccount the combined effects of the above parameters, iwill be necessary to compare experimental results for thesame engine operating conditions in terms of the relativeequivalence ratio so as to ensure that the blendcombustion process takes place with the same excess aivalues with respect to the fuel mass injected per cycle.

Table 2. Properties of fuels

PropertiesDiesel

fuelRME

Cetane number 48 52

C/H/O (molar fraction) 16:30:0 19:34:2

Density, g/cm3 (15 C) 0.83 0.89

Viscosity, cSt (37.8 C) 3.3 4.5

Net heating value, kJ/kg 43000 36000

Carbon content C (wt%) 86.5 77.4

Hydrogen content H (wt%) 13.4 12

Oxygen content O (wt%) - 10.5Sulphur content S (wt%) 0.05 < 0.01

Stoichiometric ratio A/F 14.5 12.6

Iodine number, g I2/100g - 118

Distillation curve

10% EV. 181 332

50% EV. 255 340

90% EV. 337 350

F.B.P. 372 353

Carbon residue (wt%) 0.01 0.05

Biodegradable no yes QQ

reli=

st


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Figure 2. Torque vs and

To clarify this, Figs. 2-4 compare the experimental resultsaccording to both the equivalence ratio and the relativeequivalence ratio referred to the test conditionsillustrated in Tab. 3.

Figure 3. Power vs and

Figure 4. Specific fuel consumption vs and and specific heat consumption vs

Table 3. Test Conditions

RPM 1 (min) 2 3 4 5 6

diesel fuel 3000 1.63 1.68 1.99 2.75 3.15 3.76

RME 3000 1.59 1.67 1.97 2.74 3.15 3.75


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These figures present the torque, power and specificconsumption respectively for the above test conditions.For the various fuel properties, whenever the comparisonis made for the same equivalence ratio value, we observea marked difference in the curves (Figs. 2a, 3a and 4a),which stresses how the performance of biodiesel isclearly lower (about 20-25%) than that obtained fromdiesel fuel, when the same quantity of air and fuel isintroduced into the cylinder. As expected, this differencetends to cancel itself out if we refer to the relativeequivalence ratio (Figs. 2b, 3b and 4b).

A major difference obviously remains, and especially athigher loads ( = 1.5-2), between the specificconsumption curves (Fig. 4b) as this parameter is bydefinition inversely proportional to the lower heatingvalue. Therefore, in order to compare diesel fuel andbiodiesel provides, specific heat consumption must beconsidered. This comparison results in entirely coincidentslopes of the plotted curves, as shown in Fig. 4c.

EMISSIONS Figures 5, 6 and 7 report the experimentalresults for the regulated exhaust emissions referred to

the test plan specified in Tab. 3.

In particular figure 5 shows the measured trend of COemissions as a function of the relative equivalence ratio.This diagram confirms the typical trend of this pollutant,sharply increasing as decreases, i.e. as the loadincreases. More specifically, these engine operatingconditions the experimental data point out significantdifferences in CO concentration between the two fuelsand a slight reduction of this pollutant when biofuel isused.

Figure 5. Emissions of CO vs

Similar considerations can be made if we examine thediagram regarding smoke emission (reported in figure 6),expressed in Bosch units and measured under the sameengine operating conditions. Here too we observe a clearreduction in smoke emissions for all values of whenbiodiesel is used.

Figure 6. Emissions of Smoke vs

Figure 7. Emissions of NOX vs

Finally, figure 7 shows the trend of emissions of nitrogenoxides. These diagrams highlight the typical bell-shapedtrend as varies. Unlike the case of carbon monoxidethe concentrations of nitrogen oxides are significantlyaffected by the type of fuel used. For instance, theconcentrations of NOx in the exhaust gas riseconsiderably, especially at higher load values, whenbiofuel is used. This can presumably be attributed to adifferent trend of heat release in the combustion chamber

which results in a proportionally different thermahistory of combustion products, on which the formationmechanism of this pollutant is notoriously dependentConsequently, in order to verify this hypothesis, wecarried out an experimental study on the evolution of thecombustion process by analyzing heat release rate in theabove specified test conditions.


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HEAT RELEASE ANALYSIS

A detailed experimental description of combustionevolution in Diesel engines is extremely complexbecause of the simultaneous formation and oxidation ofair/fuel mixture.

Moreover, knowledge of the combustion process, even inglobal terms, is extremely useful if we are to betterunderstand the mechanisms governing a greater or

lesser concentration of pollutants in the exhaust gas.Heat release analysis therefore makes it possible toassess, at least globally, the effects that the variousblends have on the combustion process. In particular, theresults of the heat release analysis are hereafter used toanalyze the trends of NOx emissions according to the fuelused (pure biodiesel and pure diesel fuel).

The trend of heat release (instantaneous rate andintegral curve) in a D.I. Diesel engine can be obtained byprocessing in-cylinder pressure data and using differentkinds of inverse single-zone models [9, 10, 11]. Theapproach followed in the present paper, defined in the

technical literature as the simple air model, isessentially based on the application of the firstThermodynamics Law.

The following fundamental assumptions have beenmade:

Quasi steady-state process;

Uniform composition of the gas inside the cylinder;

Uniform distribution of thermodynamic properties;

No dissociation of the chemical compounds presentafter combustion;

Specific heats of the gaseous mixture are calculatedas a function of temperature;

The cylinder is considered as a closed system withrespect to the fuel injected mass rate.

With specific reference to D.I. Diesel internal combustionengines, we must also assume that the wholecombustion process develops according to the meanvalue of the equivalence ratio.

The heat release rate is thus directly expressed by theequation:

In accordance with the above hypotheses, thecombustion process can be considered as an equivalentexternal heat flux (not due to the oxidation of the injectedfuel) which causes a variation of internal energy U in thesystem. Consequently, the first thermodynamic law canbe rewritten as follows:

In this way the difference between the heat globallyreleased (positive) and the heat lost through the cylindewalls (negative) yields the net heat release, whichassumes a particular physical significance. As thisquantity can be directly derived from the experimentapressure data, it represents the portion of heat energypotentially introduced with the fuel that can be effectivelyconverted into mechanical work.

The term U for the gas internal energy (assumed tobehave as a perfect gas) is provided by:

which, under the no loss hypothesis and considering thefuel already introduced into the cylinder at intake valveclosing, can be reduced to:

Imposing mass conservation (no blow-by leakage), thedifferential form of the gas state equation is:

Finally, combining the previous equations, we can write:

The latter relation makes it possible to calculate theinstantaneous net heat release rate; all the quantities onthe right hand side are known or can be easily derivedonce the indicated pressure cycle has been measured.

Therefore, if we want to determine gross heat releasestarting from the net heat release, the heat transferthrough the wall has to be evaluated:

The technical literature contains several correlations foevaluating the heat transfer coefficient but the only onespecifically developed for D.I. Diesel engines is theHohenberg's relation [12]:

in which C1 and C2 are tuned constants for which thevalues of 130 and 1.4 have been respectively assumedas recommended by Hohenberg himself on the basis of awide experimental investigation.

ddQ

ddU

ddVp

ddQ

ddQ

ddQ wwng ++=+=

d

dU

d

dVp

d

dQ

d

dQ

d

dQ wgn +==

d

dTmc

d

dmTc

d

dUvv +=

d

dTmc

d

dUv=

d

dT

Td

dV

Vd

dp

p

111=+

d

dU

d

dV

pd

dQ

d

dQ

d

dQ wgn+==

)(.

wgw TThSQ =

8.0

2

_4.08.006.0

1 )( CvTpVCh p +=


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Figures 8-10 show the net heat release rate diagrams forthree different operating conditions ( = 3.75, = 3.15and = 1.61) for pure diesel fuel and pure methyl ester,respectively.

Figure 8. Heat release rate vs crank angle degree



These figures point out that the heat release rate initiallyfollows a downward trend, corresponding to the end ofcompression stroke which suddenly changes slope atcombustion starting. By analyzing these diagrams wecan observe that when the engine is fueled withbiodiesel, the process starts in advance in all operatingconditions, a feature which becomes more evident as theload increases. This determines a similar trend in themean temperature variation rate of gases in the cylinderas shown in figures 11-13. Therefore, depending on the

fuel used, the maximum temperature increase rate isfound at somewhat different engine crank anglepositions. In particular, compared with the operatingconditions tested using diesel fuel, when biodiesel isused the temperature variation rate peaks at a positioncloser to piston top dead center.

Figure 11. Gases mean temperature variation rate vscrank angle degree



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This different behavior obviously determines a differentthermal history of the gases in the cylinder for the same

value of , shown in figures 14-16.

Figure 14. Gases mean temperature vs crank angle degree



These figures show the trend of the instantaneous meantemperature of the gases in an interval of the crank angleinvolving the whole combustion process. On the basis of

these observations and the analysis of the diagrams infigures 11-13, it can be understood how biodiesecombustion determines an in-cylinder thermal historythat is not only in advance but also characterized byhigher absolute values of the mean temperature peaksespecially as the load increases. Although theseobservations are made in terms of gas meantemperature values, they are nevertheless clearlyindicative of corresponding increases in the temperatureslocally reached in the combustion chamber, on which thereaction rate of nitrogen oxide formation typicallydepends. In order to identify the causes of this advancedheat release, observed for all operating conditions

accurate measurements of the instantaneous injectionpressure and the injector needle lift have been taken.

Figures 17-19 show the trends of these quantities underthe same test conditions. Here too, for the abovereasons, a comparison at the same relative equivalenceratio has been made in order to reproduce the sameenergy release conditions. The diagrams plotted in thesefigures show that fuel injection starts considerably inadvance when biodiesel is used. This higher advancevalue is clearly determined by a faster increase in theinjection pressure, as can be seen in the diagrams. Thereason why the injection system behaves in this way lies

primarily in the different modulus of elasticity caused bythe differing densities of the two fuels. Indeed, althoughthe properties of RME are very similar to those of diesefuel, the methyl ester has a slightly higher density (Tab. 2which affects the fuel compression process in thevolumetric injection pump. Thus, for the same variation inthe volume created by the first part of the pump strokethe higher density of biodiesel causes a faster increase ininjection pressure. In addition to this phenomenon, thereis also a different quantity of fuel injected per stroke fothe same value of , although this factor is much lessmarked. In conclusion, when biofuel is used, the increase


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in NOx emissions seems to be fundamentally determinedby an operating mode of the injection pump which causesa premature needle lift compared to the nominalconditions when the engine is fueled with diesel fuel.

Figure 17. Needle lift and fuel injection pressure vs

crank angle degree

Figure 18. Needle lift and fuel injection pressure vscrank angle degree

This behavior results in an equally premature release ofheat which, as we have seen above, generates highertemperatures inside the cylinder during the combustion

process. Therefore, it is reasonable to assume that if wemodify the injection system so as to restore the nominaladvance conditions, the phenomenon will be eliminatedor drastically reduced so as to return the NOx emissionsto comparable values, regardless of the fuel used.

The difficulty in adapting the operating conditions oftraditional mechanical injection systems to the kind offuel used (biodiesel or biodiesel-diesel fuel blends) canbe easily overcome by employing electronically controlledinjection pumps such as the recent Common Railinjection system [13, 14]. By adopting this solution, the

control unit could assign the optimal injection advancevalue according to the composition of the biodiesel-diesefuel blend by making reference to a given map drawn upa priori in the laboratory.

Figure 19. Needle lift and fuel injection pressure vscrank angle degree

CONCLUSION

Biodiesel fuel has attracted considerable attention inrecent years because of both its environmentally friendlycharacteristics (biodegradability) and its lowenvironmental impact in terms of net global release ocarbon dioxide.

Biodiesel assumed an even more important role after therecent world conferences (Kyoto '97 and Buenos Aires'98) on the question of global warming, during which the

international community guaranteed to reduce emissionsof greenhouse gases by 5% compared to 1990 levels bythe year 2010.

Moreover, biodiesel does not contain sulfur and istherefore already compatible with the limits foreseen forthe year 2005 (< 50 ppm) whereas diesel fuel will have toundergo a more rigorous and expensive desulfurisationprocess.

This research has proved the good overall behavior obiodiesel, in terms of both performance and exhaustemissions, even if the reduction in some pollutants (COand particulates) has been accompanied by more or lessmarked observations of higher concentrations of NOxcompared to diesel fuel fueled engines.

In order to reach a more detailed understanding of thedependence of nitrogen oxides on the type of fuel used, afurther experimental investigation has been performedfuelling the engine with pure biodiesel and pure diesefuel according to the test plan reported in table 3.

The results of these experiments can be summarized asfollows:


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Confirming previous results [3, 4, 5], engineperformance (torque, power) is substantiallyunaffected if the biodiesel and the diesel fuel arecompared in terms of the relative equivalence ratio inorder to take into account the different lower heatingvalue and the stoichiometric ratio.

The same considerations can be made for fuelconsumption if the two fuels are compared in termsof specific heat consumption.

In both cases the emissions of carbon monoxide andcarbon particulates, here measured as smoke inBosch units, have the typical sharply rising trend as falls, i.e. as the load increases. In these engineoperating conditions the experimental data forbiodiesel points to an appreciable drop inconcentrations of both types of pollutants.

The concentrations of nitrogen oxides show asignificant increase (up to around 20% in half loadconditions) compared to the values of engine fueledwith diesel fuel. This can be essentially attributed to adifferent evolution of the combustion process, to

which the NOx formation mechanism is typicallyrelated. In order to follow the evolution of thecombustion process (in global terms) we analyzedthe heat release obtained from measurements ofindicated pressure cycles.

This analysis, performed for all the engine operatingconditions, showed that, in the case of biodiesel, heatrelease always takes place in advance with respectto T.D.C. (between 3 and 5 degrees) compared towhen the engine is fueled with diesel fuel. This leadsto a similar advance in the variation rate of the meangas temperature in the cylinder which, in turn and for

the same value of , results in a different thermalhistory of the burnt gases. This behavior determinesconsistently higher peaks in the mean temperaturesreached in the combustion chamber and, hence, therelated to the higher concentrations of nitrogenoxides measured in the exhaust gas.

The measurement of both instantaneous injectionpressure and injector needle lift showed a greateradvance in the fuel injection process when biodieselwas used. There are two reasons for this behavior:the first and predominant factor concerns thedifferent densities of the two fuels; the second is the

different quantity of injected mass per cycle.We can deduce from the above considerations that thehigher concentrations of NOx detected when the enginewas fueled with biodiesel do not seem to be primarily dueto the characteristics of the fuel but, rather, to theoperation of the injection system (increased injectionadvance).

ACKNOWLEDGMENTS

A sincere thanks to Novaol s.r.l. for RME supply:

REFERENCES

1. P. Andreini, L. Galbiati "La strategia europea eitaliana per lambiente e per la riduzione di CO2" LaTermotecnica, marzo 1998

2. Decreto Ministeriale n. 219 del 22 maggio 1998pubblicato sulla G.U. d. R.I. n. 158 del 9.7.1998.

3. V. Rocco, M.V. Prati, A. Senatore, E. Cerri, MBenfenati "Fuelling a Small Diesel Engine by UsingDiesel fuel and RME: Comparative Results andParticulate Characterization" 1 ConvegnoInternazionale sui Carburanti Alternativi e Combustibili, Lecce 1996

4. V. Rocco, R. Montanari, M.V. Prati, A. Senatore"Analysis of Particulate Emitted from an IDTurbocharged Small Diesel Engine Fuelled withDiesel Fuel, Biofuel and their Blend" 1995 FalTechnical Conference Volume 3 ASME, 1995.

5. M. Cardone, M.V. Prati, V. Rocco, A. Senatore"Analisi Sperimentale delle Prestazioni e delleEmissioni di un Motore Diesel Alimentato conMiscele di Biocombustibile e Gasolio" MIS-MAC VMetodi di Sperimentazione nelle Macchine, Roma13 febbraio 1998

6. S. Howell U.S. Biodiesel Standards-An Update ocurrent activities SAE Paper 971687, 1997

7. J.H. Van Gerpen et alt. Determining the influence ocontaminants on Biodiesel Properties SAE Paper n971685, 1997

8. X. Montagne Introduction of rapeseed methyl Estein Diesel Fuel - The French National Program SAE

Paper n. 962065, 19959. J.B. Heywood "Internal Combustion Engine

Fundamentals" Mc Graw - Hill Book Company, 1988

10. V. Rocco "D.I. Diesel Engine In-Cylinder PressureData Analysis Under T.D.C. Setting Error" SAE Papen. 930595, 1993

11. D. Laforgia "Biodiesel Fueled I.D.I EnginesPerformances, Emissions and Heat ReleaseInvestigation" 1 Convegno Internazionale suCarburanti Alternativi e i Combustibili, Lecce 1996

12. G.F. Hohenberg "Advanced Approaches for HeaTransfer Calculations" SAE Paper n. 790825, 1979

13. G. Stumpp, M. Riccio "Common Rail - An AttractiveFuel Injection System for Passenger Car DI DieseEngines" SAE Paper n.960870, 1996

14. W. Boehner, K. Hummel "Common Rail InjectionSystem for Commercial Diesel Vehicles" SAE Papern:970345, 1997

15. J. Krahl, A. Munack, M. Bahadir, L. Schumacher, NElser "Reveiw: Utilization of Rapeseed Oil, RapeseedOil Methyl Ester or Diesel Fuel: Exhaust GasEmissions and Estimation of Environmental Effects"SAE Paper n. 962096, 1996


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CONTACT

Prof. Adolfo SenatoreDIME Dipartimento di Ingegneria Meccanica perlEnergetica - Universit di Napoli Federico IIvia Claudio, 21 Napoli 80125 ItalyPhone: 0039-081-7683276Fax: 0039-081-2394165e-mail: [email protected]

DEFINITIONS, ACRONYMS, ABBREVIATIONS

RME: Rapeseed Methyl EstersASTM: American Society for Testing and Material

di with biodiesel

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