variation of co , hc, no emissions for an euro iii engine under … · 2012-12-10 · variation of...

Variation of CO2, HC, NOX Emissions for an EURO III Engine underUrban Traffic Conditions

TOKAR ADRIANA, NEGOITESCU ARINAFaculty of Civil Engineering

University Politehnica of Timisoara2 Traian Lalescu Street, 300223 Timisoara

ROMANIAMechanical Machines, Technology and Transportation Department

University „Politehnica” of Timişoara1 Mihai Viteazu Blv., 300222 Timisoara

[email protected], [email protected]

Abstract: - In the experimental study were controlled CO2, HC and NOx emissions resulted from combustioninto the engine which equips the Dacia Logan 1.4 MPI EURO III car. The experimental simulation of runningin traffic conditions was performed on the LPS 3000 chassis dynamometer together with the AVL DiCom 4000gas analyzer in order to measure the pollutant emissions. Different experimental situations in traffic operationwere simulated by activating the stand LPS 3000 braking system, maintaining a constant traction F=0N andF=200N. The tests were accomplished in the Road Vehicles Laboratory from University Politehnica ofTimişoara. It was noticed that high CO2 and NOx values were recorded in the fuel rich mixtures areas and highHC values in the poor mixtures area.Key-Words: - pollutant emissions, chassis dynamometer, gas analyzer, vehicle, traffic conditions

1 IntroductionRoad transports achieved by vehicles equipped

with internal combustion engines have an importantcontribution to environmental pollution, practicallyaffecting all ecosystems.

It is noted that the transport means (frommotorcycles to airplanes) produce 74% CO, 61%NOx and 21% CO2, their contribution to theparticles emission being relatively small.

Fig. 1 Analysis of pollution in EU related to the fleet of carsa) CO; b) NOx; c) HC

a b

c

WSEAS TRANSACTIONS on HEAT and MASS TRANSFER Tokar Adriana, Negoitescu Arina

E-ISSN: 2224-3461 37 Issue 2, Volume 7, April 2012

If only pollution transport is considered (Fig. 1),it can be observed that CO and HC emissions are inparticular due to gasoline engines (spark ignitionengine). The particles emission is generated almostentirely by diesel engines (compression ignitionengine), while the overall NOx emission is dividedrelatively evenly between gasoline and diesel. As itwas mentioned, the most dangerous pollution effectsfrom internal combustion engines occur in theatmosphere through the harmful gases emission.

Compounds that are formed in the exhaust gasescontribute to air pollution both globally and locally,directly or indirectly due to chemical reactions inthe atmosphere [7]. The atmosphere localcomposition change can produce effects on thepopulation health, such as those produced by theCO, particles and ozone emissions. On the entireplanet, the increase of the gases concentration thatproduces the greenhouse effect, will lead to globalwarming, with unpredictable consequences on theenvironment and life.

Hydrocarbons category includes gaseousproducts of incomplete combustion and fuelcomponents that can vaporize. Chemical compoundsconsist of many elements that exist in the fuel andwhich are passing unchanged through the engine.There are differences in the composition ofhydrocarbons from the gasoline and diesel enginesexhaust gases; generally, diesel contains a greaterproportion of hydrocarbons with higher molecularweight.

Nitrogen oxides are formed through the reactionbetween atmospheric oxygen and nitrogen at highpressures and temperatures, specific to combustionchamber. As temperature increases, the NOxproportion in the exhaust gases also increases.Among various oxides, NO represents the mainconstituent. In exhaust gases a certain amount ofnitrogen dioxide, NO2 is also present, quantitywhich increases when NO is exhausted into theatmosphere, by its supplementary oxidation. NO2 isgenerally considered the most important for humanhealth, therefore rules and standards are oftenexpressed with direct reference to NO2 and not toNOx general category. From the proportion point ofview NOx emissions represent the secondcomponent which contributes to the greenhouseeffect after CO2 and also have an importantcontribution to photochemical smog formation [8].

Carbon dioxide does not play a significant role inozone production and is non-toxic. It contributes ina 50% rate to the greenhouse effect, because itabsorbs the energy radiated by the earth surface.Although is not a toxic emission, carbon dioxide,CO2 is recently considered as the most dangerous

pollutant of our planet, disturbing the climate,melting eternal ice and icebergs through thegreenhouse effect that it produces. It was calculatedthat cars exhaust into the atmosphere about 4 tonesof CO2 per year and km2. Without taking intoaccount the carbon dioxide role in thephotosynthesis process and the action of plantchlorophyll, it can be shown that only human breathproduces annually 300kg CO2 per person which fora density of 100 inhabitants per km2 leads to 30t peryear. This means that, within acceptable limits, thecar produces 12% carbon dioxide emissions, whichcan not currently be considered as a disaster, but canbecome, given the increasing motorization trends[2].

2 The Experimental Stand for VehicleTesting

Besides standard on-board devices, measuring,acquisition and processing devices for additionaldata were installed in order to obtain the requiredinformation concerning the tested car quality and torecord as precise as possible the test results indigital, analog, or graphics form (Fig. 2).

The correct measurement method selection, theuse of the most adequate measurements, dataacquisition and storage instrumentation, the mostperforming data processing software and the properdesign of the measurement chain represent theprincipal condition in order to obtain reliable testresults. There also have been provided optimaloperation conditions of the entire measurementchain by isolation against vibration, protection fromenvironment excessive actions, adequate voltagesupply, etc [2], [6].

The testing stand achievement involved themeasuring and driving conditions simulationequipment adaptation in accordance to the urbantraffic. An experimental simulation method ofrunning under traffic conditions using dynamometertesting correlated with gas analyzer for pollutantsmeasurements was achieved.

LPS3000 permits the engine performancestesting [4]. The simulation on the ChassisDynamometer is performed with an eddy currentbraking system. The air-cooling fan connected to thecommunication console is operated by radio remotecontrol and allows the drag simulation. Forsampling the exhausted emissions during theexperimental tests, AVL Dicom 4000 analyzer fromthe laboratory instrumentation was used (Fig. 3) [3].



Figure 2 Experimental standa - testing equipment, b - vehicle positioning on the chassis dynamometer

Fig. 3 Dicom 4000 gas analyzera - analyzer image; b- measurement sensors

3. LPS 3000 Software ComputingData

In "constant speed" operation mode, thedynamometer is adjusted to maintain a constantspeed, irrespective of vehicle traction (fromminimum to maximum throttle). Only the presetspeed can be used. Eddy current braking systemefficiency increases up to the maximum throttle, butnot the speed.

Running conditions simulation with LPS3000software was accomplished for the followingconditions [4]:

- The power at the wheel calculation [kW].Power at wheel has multiple links with vehicle stateparameters.

frtrmii

LTRTncp

min0

0tr 130

)VP (1)

Where:Vt [m3] – The engine total cylinder capacity(volume)p0 [bar] – The ambient pressureci [J/kg·K] – The fuel inferior heat capacityn [rot/min] – The speed



τ [-]– The engine strokesR [J/kg·K] – The thermodynamic constant of thedriving fluidt0 [ºC] – The ambient temperatureλ [-] – The air excess coefficientLmin [kg/kg] – The stoichiometric air quantityrequired to burn 1 kilo of fuelηi [%] – The indicated efficiencyηm [%] – The mechanical efficiencyηtr [%] – The transmission efficiencyηfr [%] – The coefficient that takes into account thepossible brakes power losses

- The drag calculation.The drag calculation relation is:

mref

Roll

ref

Flex

ref

Airx a

vP

vvP

vvP

F

33

26,3 (2)

Where:vref [km/h] – The reference speed for drag values(normally equal to 90 km/h);v [km/h] – The driving speed;Pair [kW] – The air resistance power;PFlex [kW] – The flex power;Proll [kW] – The roller resistance power;am [kg] – The vehicle weight.

- The air resistance power calculation [kW]The air resistance power is proportional to thevehicle front surface and air resistance coefficientcw:

vvvAcP FrontwAir 205,0 (3)

Where:The air density ρ = 1.1 kg/m³The air resistance coefficient Cw = 0.38The vehicle front surface AFront = 1.7m x1.5 m = 2.55m²The driving speed v = 50km/hThe head wind speed v0 = 0m/s

- The roller resistance power calculation [kW]The roller resistance power occurs due to tire androad surface deformation as a speed function.

vgmP rRoll (4)

Where:The tires to roller resistance coefficient

μr=0.012The vehicle weight m = 1100kgThe gravitational constant g = 9.81m/s²The driving speed v = 50km/h

Since the roller resistance power represents onlya small fraction of the total road load it is consideredas a fixed standard value for the dynamometers inquestion: for steel belted radial tires the power is ofapprox. 2,5kW and for winter tires approx. 3,5kW.Defining the vehicle weight, aerodynamic dragpower and rolling resistance power are absolutelynecessary for road load simulation.

- The vehicle weightThis value is necessary in order to obtain aproportional traction force depending on the eddycurrent braking system from the vehicle determinedacceleration.

F=m∙a [N] (5)

- The torque calculation

M=P [kW]∙9549/n [rot/min] (6)

- The engine power prediction for gasolineengines

DIN 70020

5,0

293][

][1013

KTmbarp

Ka

EWG 80/1269

6,02,1

298][

][990

KTmbarp

Ka

ISO 15856,02,1

298][

][990

KTmbarp

Ka

SAE J1349

6,02,1

298][

][990

KTmbarp

Ka

JIS D1001

6,02,1

298][

][990

KTmbarp

Ka

Where:The correction factor Ka = 1.07671The atmospheric pressure at the dynamometer, inmbar (1mbar = 0.001bar)The air temperature at the dynamometer, inKelvin degrees (0°C = 273K)The values of these parameters are:The ambient air pressure p = 936mbarThe ambient temperature T = 17°C = 290K

- The pressure behavior at overload

E

L

PPr (7)



- The specific fuel consumption (for 4 strokeengine) based on SAE J1349 is calculated with therelation:

nDFq

120000 (8)

Where:fm – The engine factorr – The pressure ratio at overloadq – The specific fuel consumption based on SAEJ1349pL – The absolute boost pressurepE – The absolute pressure before the compressorF – The fuel flowD – The cylinder diametern – The engine speed

4. Experimental ResultsExperimental researches were performed in the

Road Vehicles Laboratory at the PolitehnicaUniversity of Timisoara. In order to achieve theexperimental researches, the operation of DaciaLogan 1.4 MPI-EURO III was controlled. Thevehicle technical characteristics are:

- The total cylinder capacity 1390 cm3

- The cylinder number 4L- The maximum power 55kW- The manufacturing year 2003- The maximum weight 1100kg- The maximum torque 112 Nm- The mileage 70518km- The ITP number 2- The urban consumption 9.2l/100km- The extra urban consumption 5.5l/100km- The mixt consumption 6.8l/100km

Experimental researches are based on the controlof major pollutants resulted from combustion intothe engine which equips the tested vehicle.

The stand simulation of the vehicle runningunder urban traffic conditions was achieved byfollowing the next steps:

- Setting the speed in constant speed module:constant and variable speed;- Setting the force in constant traction module:F=200N;- The air conditioned unit: turned off.The experimental stand allows the recording of

atmospheric conditions which correspond tomeasurements moment:

- The ambient temperature ta=27.8 C

- The intake air temperature ti=26.5 C- The air humidity φ=39.9%- The air pressure pa=1019.6 hPa- The steam pressure ps=14.9 hPa

As a result of the urban traffic conditionssimulation on the test stand, the values of thevehicle emissions were recorded depending both onthe engine speed and excess air coefficient (λ).

With the operating mode Constant Speed thedynomometer is regulated in such a way that thedriving speed remains constant independent fromthe traction (from low to full throttle), i.e. only thespeed which was pre-set can be driven. Only theeddy curent brake effectiveness increases up to fullthrottle but not the speed. A pre-set traction valueactivates the eddy-current brake immediately whichmaintains a constant traction for the duration of themeasurement. The values to be set are oriented on:

- The test vehicle model and sizes;- The desired inclination angle.In order to run the tested vehicle up to the

operating temperature an inclined surface balancewas simulate. The simulated slope can be drived inany gear. Eddy current brake effectiveness remainsconstant at all speeds.

When vehicle runs at variable speed, CO2emissions shows a continuous increase under thesame engine operating conditions (Fig.4). Thevariation of CO2 emission values is increasing for arange between 14.5-16% when the vehicle operateson speeds lower than 2300rpm to constant speed,50km/h (Fig 5) and after this speed value it can beobserved that CO2 emission values are almost thesame.

From Fig. 6 and Fig. 7 it can be observed thatHC emissions show a fast reduction up to around2300rpm. After this speed value the HCconcentrations record close and low values (between10-20ppm).

The NOx emission variation for an continuousincreasing of the engine speed shows a smallincrease when the speed is constant (Fig. 6) andrecords similar values with a small decreasing trendwhile the speed varies (Fig. 7).

By analysing the two cases (constant andvariablepeed) it can be observed that the CO2emissions have similar values. For NOx and HCcase, operating at variable speed leads to an increaseof these emissions.

Emissions of CO and O2 record high values atstart and decrease while the engine speed decreasesas it is shown in Fig.8 and Fig. 9.



Fig. 4 CO2 variation law versus the speed, F=200N (constant speed)

Fig. 5 CO2 variation law versus the speed, F=200N (variable speed)



Fig. 6 HC and NOx variation law versus the speed, F=200N (constant speed)

Fig. 7 HC and NOx variation law versus the speed, F=200N (variable speed)



Fig. 8 CO and O2 variation law versus the speed, F=200N (constant speed)

Fig. 9 CO and O2 variation law versus the speed, F=200N (variable speed)



Fig. 10 CO2 variation law versus the λ, F=200N (air conditioning unit turned on/off)

Fig. 11 HC variation law versus the λ, F=200N (air conditioning unit turned on/off)

Fig. 12 NOx variation law versus the λ, F=200N (air conditioning unit turned on/off)



The LOGAN 1.4MPI vehicle running simulationon the test stand which was loaded at 200N wasaccomplished in order to compare thepollutantemissions for the case of air condinioning unitturned on/off.

In Fig. 10, Fig. 11 and Fig.12 were comparativeplotted the variations of CO2, HC and NOx versusthe excess air coefficient for analyzing the inflenceof the mixture qulity on the emissions concentrationexhausted during the engine operation under trafficconditions. In the lean mixtures area, the exhaustedCO2 and NOx are smaller due to the a smaller fuelconsumption. In this mixture area values HC valueincreases. By the speed limitation in accordance tothe urban traffic one and by maintaining the tractionconstant, F=200N, real traffic conditions weresimulated and pollutant emissions were controlled inorder to evaluate the vehicle operation for load case[1].

5 ConclusionDuring tests performed on the chassis

dynamometer the pollutant emission values weremeasured, values which are different from oneoperation mode to another.

It can be observed that at constant speedmovement, vehicles equipped with gasoline engineare exhausting pollutants emissions at the lowestlevels. By setting the speed value at 50 km/h therunning conditions similar to urban traffic wereimposed. The urban traffic can not provide movingat constant speed, thus for urban traffic remains toexploit the vehicle in the most polluting operationmodes. The start off and idling operation modeswere used in order to simulate traffic jams andstationary at traffic lights. Following the start up andacceleration simulation, the engine burns better thefuel of the lean mixture (λ>1,05-1,2), but exhausts anitrogen oxides significant amount due to theincrease of speed and temperature in the combustionchamber, resulting the increase of thermalefficiency. On deceleration, the engine speed andcombustion temperature decrease occurring themixture enrichment, which leads to incompletecombustion, power reduction and specific fuelconsumption increase. Thus the emitted pollutantsduring this operation mode consist of largequantities of unburned hydrocarbons andconsiderable quantities of carbon monoxide.

References:[1] Tokar, A., Researches Regarding the InteractionBetween Internal Combustion Engines and

Environment, PhD Thesis, Politehnica University ofTimişoara, Romania, 2009[2] Negrea, V.D., Processes in Internal CombustionEngines. Economicity. Pollution Reduction.,Volume II, Politehnica Publishing House,Timişoara, 2003.[3] ***, AVL DiCom4000 User Manual version1.01, AVL LIST GMBH, Graz, Austria, 1998.[4] ***, Chassis Dynamometer LPS3000 - StandardOperating Instructions and User Manual, MAHAMaschinenbau Haldenwang GmbH&Co.KG, 87490Haldenwang, Germany, 2003.[5] TOKAR A., NEGOITESCU A. ComparativeAnalysis of Exhausted Gases Opacity under UrbanTraffic Conditions, 8th IASME /WSEASInternational Conference on Fluid Mechanics &Aerodynamics (FMA '10) 8th IASME /WSEASInternational Conference on Heat transfer, thermalEngineering and Environment (HTE '10), NewAspects of Fluid Mechanics, Heat Transfer andEnvironment, ISSN: 1792-4596 ISBN: 978-960-474-215-8., pp. 209 – 213, Taipei, Taiwan August20-22, 2010[6] R. S. Sokhi, Urban air quality, AtmosphericEnvironment, Fifth International Conference onUrban Air Quality, Volume 42, Issue 17, Valencia,Spain, 29-31 March 2005, pp. 3909 – 3910.[7] COFARU C. Strategies of Urban PollutionDiminishing by Controlling Emissions ofAutomotive Engines, Latest Trends on UrbanPlanning and Transportation 3rd WSEASInternational Conference on URBAN PLANNINGAND TRANSPORTATION (UPT '10), ISSN: 1792-4286, ISBN: 978-960-474-204-2, pp. 76-81,Corfu Island, Greece, July 22-24, 2010



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