NASA Technical Reports Server (NTRS) 20120001788: Evolution of Combustion-Generated Particles at Tropospheric Conditions

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NASA/TM—2012-217257 GT2010-23689
Evolution of Combustion-Generated Particles at
Tropospheric Conditions
Kathleen M. Tacina and Christopher M. Heath
Glenn Research Center, Cleveland, Ohio
January 2012
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NASA/TM—2012-217257 GT2010-23689
Evolution of Combustion-Generated Particles at
Tropospheric Conditions
Kathleen M. Tacina and Christopher M. Heath
Glenn Research Center, Cleveland, Ohio
Prepared for the
Turbo Expo 2010
sponsored by the American Society of Mechanical Engineers (ASME)
Glasgow, Scotland, United Kingdom, June 14–18, 2010
National Aeronautics and
Space Administration
Glenn Research Center
Cleveland, Ohio 44135
January 2012
Acknowledgments
This research was funded by NASA’s Fundamental Aeronautics/
Subsonic Fixed Wing and Fundamental Aeronautics/Supersonics program.
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only. Their usage does not constitute an offi cial endorsement,
either expressed or implied, by the National Aeronautics and
Space Administration.
This work was sponsored by the Fundamental Aeronautics Program
at the NASA Glenn Research Center.
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Available electronically at http://www.sti.nasa.gov
Evolution of Combustion-Generated Particles at
Tropospheric Conditions

Kathleen M. Tacina and Christopher M. Heath
National Aeronautics and Space Administration
Glenn Research Center
Cleveland, Ohio 44135
ABSTRACT m Massflux
Thispaperdescribesparticleevolutionmeasurementstaken
Q Volumeflux
intheParticulateAerosolLaboratory(PAL).ThePALconsistsof
aburnercapableofburningjetfuelthatexhaustsintoanaltitude R Richardsonnumber
chamber that can simulate temperature and pressure conditions r Radialcoordinate
up to 13,700 m. After presenting results from initial tempera-
Re Reynoldsnumber
ture distributions inside the chamber, particle count data mea-
sured in the altitude chamber are shown. Initial particle count T Temperature
datashowthatthesamplingsystemcanhaveasignificanteffect
u Velocity
on the measured particle distribution: both the value of particle
numberconcentrationandtheshapeoftheradialdistributionof x Axialdistancefromthejetexitplane
the particle number concentration depend on whether the mea-
x Axialdistancefromthevirtualorigintothejetexitplane
E
surementprobeisheatedorunheated.
ρ Density
θ Normalizedtemperaturedifference, T−T∞
Nomenclature T0−T∞
B Buoyancyflux ζ Particlenumberconcentration
d Nozzlediameter Subscripts
0
(cid:113)
d∗ Equivalentsourcediameter,d∗=d ρ0 0 Nozzleexit
0 ρ∞
CL Centerline
g Gravitationalconstant
∞ Chamber
J Momentumflux
l Coflowlengthscale
c
l Mortonlengthscale
M
NASA/TM—2012-217257 1
Toaltitudeexhaust
Nottoscale
139.7
132.08
121.92
111.76
101.6
91.44
81.28
71.12
60.96
50.8
40.64
30.48 gFarsomsupcoplldy
20.32
10.16
0
-5.08
CombustionChamberCasing
TransitionPipe CMhaixminbger CComhabmusbteiorn FAuteolAmiirzation
MainAir
(a) (b)
FIGURE 1: The Particulate Aerosol Laboratory: (a)sketch and (b)photograph. Note that in (b), the burner is covered by a pressure
housing. Thegas(nitrogenorair)fromthecoldgassupplysimulatestheatmosphere,andtheburnerexhaustsimulatesaircraftengine
exhaust.
1 Introduction this unique facility, a combustor capable of burning jet fuel ex-
Although particulate emissions from aircraft engines were hausts into an altitude chamber capable of simulating tempera-
initially of concern because of the visible smoke [1,2], recent ture and pressure conditions up to 45,000 ft, allowing the par-
researchhasfocusedonthehealthandenvironmentaleffectsof ticle evolution to be studied at altitude conditions. A scanning
ultrafineparticulateemissions. Duetothenegativehealtheffects mobility particle sizer (SMPS) measures the particulate profile
ofultrafineparticles,theregulationsonparticlessmallerthan2.5 at the combustor exit and in the altitude chamber. The probe
microns have become increasingly stringent [3]; most particu- usedtosampletheexhaustplumeinthealtitudechambercanbe
latesemittedbyaircraftaresmallerthan2.5microns[1,4]. placedatdiscreteaxialpositionsthatrangefromtheexhaustnoz-
zleexittothetopofthealtitudechamber.Thispaperwillpresent
A major environmental effect of aircraft particulate emis-
initialmeasurementsoftheparticlesizedistributiontakenfrom
sionsistheireffectonthetheformationandpropertiesofcirrus
thecombustorandmeasurementsoftheparticlesizedistribution
cloudsinthetroposphere;however,thiseffectisnotwellunder-
takeninthealtitudechamber.
stood [5]. Several areas require further research, including the
microphysical and chemical processes governing the evolution
of aviationparticulates. Previous workhas sought tocharacter-
ize aircraft engine emissions using combustion rigs, on-ground 2 FacilitiesandInstrumentation
enginetests[4,6–8],andmeasurementstakenintheaircraften- 2.1 FacilityDescription
gine plumes at altitude [6]. The work described in this paper The Particulate Aerosol Laboratory (PAL) consists of a
complementstheseefforts. burner connected to an altitude chamber, as shown in Figure1.
ThispaperdescribesmeasurementstakenintheParticulate The burner is capable of burning conventional jet fuels and al-
AerosolLaboratory(PAL)atNASAGlennResearchCenter. In ternativefuelssuchasFischer-Tropsch. A1.6-mlongtransition
NASA/TM—2012-217257 2
pipeconnectstheburnerexittothealtitudechamber;thetransi-
tion pipe terminates in a 1.27-cm diameter nozzle that exhausts 270 0.10 m 1.40 m
0.30 m 6,100 m
thecombustionproductsintothealtitudechamber. Thealtitude
0.61 m 9,140 m
chamber can simulate standard day pressures and temperatures 260 0.91 m 12,190 m
uptoaltitudesof13,700m.
AsshowninFigure1a,theburneriscomposedoftwoparts: K)250
a combustion chamber and a mixing chamber. The upstream e (
ur
sectionofthecombustionchamberissurroundedbythemixing at240
er
chamber. The main combustion air enters the burner in the an- p
m
nularareabetweenthecombustionchamberandthecombustion e
T230
chambercasing. (Abulkheadpreventsmixingbetweenthemain
airinthisannularareaandthecombustionproductsinthemixing
220
chamber.) Flowingupstream,themainairentersthecombustion
zone through a 3.81-cm diameter opening in the upstream end
210
30 20 10 0 10 20 30
ofthecombustionchamber. Fuelandasmallquantityofatom-
Radial distance (cm)
ization air enter the combustion chamber through an air assist
fuel injector. The combustion products enter the mixing cham- FIGURE 2: Baseline chamber temperature distribution with the
ber through a 0.635-cm annular slot in the downstream end of burneroff.
the combustion chamber. The entire burner is surrounded by a
housing, as shown in 1b. The burner pressure is one to two at-
mospheres. sifier,andaTSImodel3085nanodifferentialmobilityanalyzer
After exiting the burner, the combustion products flow — was used to measure the particle size distribution. The CPC
through a 2.43-cm inner diameter transition pipe into the alti- wasalsousedalonetomeasuretheparticlecount.
tudechamber. Anorificeinthetransitionpipedropsthepressure A blunt-tipped sampling probe with a 0.32-cm inner diam-
of the combustion products to near the pressure of the altitude eter was inserted into the transition pipe facing normal to the
chamber.Portsinthetransitionpipeupstreamoftheorificeallow flow. This probe was used to sample the particle distribution at
combustionproductsamplestobedrawnforgasandparticulate theburnerexit. Tominimizeagglomerationandcondensationin
analysis. thesamplingsystem,thecombustionproductsweredilutedwith
A cold gas supply (nitrogen or air) provides the working drynitrogenslightlydownstreamoftheprobetip.
fluid for the altitude chamber. This working fluid simulates the Ablunt-tippedsamplingprobewasalsousedtomeasurethe
atmosphere and allows the effects of mixing between the hot particlecountinthealtitudechamber. Theprobefacewasparal-
combustorexhaustandacoldatmospheretobestudied.Nitrogen leltotheprimaryflowdirectionexceptforthemeasurementsat
wastheworkingfluidforallmeasurementsreportedhere. 0.18mdownstreamofthenozzleexitat12,190mstandardday
The chamber diameter is 0.597-m, and the height of its conditions;inthissinglecase,theprobefacewasapproximately
cylindricaltestsectionin1.83-m. Fourwindowports,each1.52- normal to the primary flow direction. This probe had a 0.4-cm
m tall by 0.102-m wide, are located 90o apart from each other. inner diameter and could be covered with heat tape to prevent
The window ports can be fitted with windows, instrumentation iceformationinsidetheprobe. Itwasconnectedtoatranslation
plates, or blanks. When a window is installed, two panes of stagethatallowedittobemovedradially.
glassareused,andthespaceinbetweenthepanesiskeptatvac-
uum;this prevents condensation on the windows and also pro-
2.3 TestConditions
vides good insulation. (When a blank or instrumentation plate
is used, it is a single thickness of aluminum and does not pro- Fourburnerconditions(seeTable1)andfouraltitudecham-
videgoodinsulation.)Forthemeasurementsreportedhere,three ber conditions were studied. The altitude chamber conditions
ports contained windows and one port contained an instrumen- corresponded to standard day temperatures and pressures at
tation plate; Figure1a shows the instrumentation plate that was 6,100 m; 9,140 m; and 12,190 m [9] as well hot day tempera-
usedduringthesemeasurements. tureandpressureconditionsat9,140m[10](seeTable2). The
chamberReynoldsnumberindicatesthattheflowwasturbulent
for all cases. As Figure2 shows, the baseline temperature in
2.2 Instrumentation the altitude chamber (when no combustion products are added)
A TSI scanning mobility particle sizer (SMPS) system isnearlyuniformexceptinthethermalboundarylayer. (Notea
model3936NL76—consistingofaTSImodel3776condensa- double-paned window is installed on the negative r side of the
tionparticlecounter(CPC),aTSImodel3080electrostaticclas- altitudechamber,andanuninsulatedinstrumentationplateisin-
NASA/TM—2012-217257 3
TABLE1: Burnerconditions
Condition Fuel/Air TotalMass l at x at
M E
Number Ratio FlowRate 6,100m 7,620m 9,140m 12,190m 6,100m 7,620m 9,140m 12,190m
kg/min m m m m cm cm cm cm
1 0.045 0.166 2.16 2.82 3.02 4.55 3.0 3.1 2.9 2.8
2 0.032 0.230 2.98 3.88 4.18 6.28 3.0 3.1 2.9 2.8
3 0.017 0.342 4.50 5.88 6.28 9.43 3.1 3.2 3.0 2.9
4 0.007 0.336 4.99 6.65 6.75 9.95 3.5 3.6 3.4 3.3
ditionsatthenozzleexit,theconditionsinthealtitudechamber,
andthetypeofflowfieldthatisestablished. Fromseveralnoz-
zlediametersdownstreamofthenozzleexittotheaxiallocation
where the effects of the altitude chamber walls become impor-
tant, theflowfieldinthePALshouldactaseitherabuoyantjet
or a momentum-dominated jet. The relative effects of jet exit
momentum and buoyancy are usually expressed in terms of the
Richardsonnumber,R,ortheratiooftheaxialdistancefromthe
nozzleexit,x,totheMortonlengthscale,l [11,12]. Theseare
M
defined in terms of the jet volume flux, Q, the jet momentum
flux,J,andthejetbuoyancyflux,B,as:
1
R= Q(B/ρ∞)2 (1)
5
(J/ρ∞)4
3
FIGURE 3: Combustion product temperature as combustion l = (J0/ρ∞)4 , (2)
M 1
products exit the nozzle into the altitude chamber at x=0. For (B0/ρ∞)2
allcasesthetemperaturerapidlyreturnedtothebaselinetemper-
where
ature as the radial distance r increased, so only the region near
∞
thenozzleexitisshown. (cid:90)
Q= u(x,r)2πrdr, (3)
0
∞
stalledatthepositiversideoftheinstrumentationchamber;this (cid:90)
B= g∆ρu(x,r)2πrdr, (4)
accountsfortheasymmetryinthetemperaturedistributionnear
thechamberwalls.) 0
Figure3 shows the temperature distribution at the nozzle (cid:90)∞
exit. Notethatthistemperaturedistributiondoesnotchangesig- J= ρu2(x,r)2πrdr, (5)
nificantly with altitude, indicating that the section of the transi- 0
tionpipethatentersthebottomofthealtitudechamberiswell-
insulated. uistheaxialvelocity, ρ isthedensity, andthesubscripts0and
∞ refer to conditions at the jet exit and in the altitude chamber,
respectively. In the jet-like limit, R and x/l are small; in the
M
3 FacilityTemperatureDistribution plume-likelimit,Rapproaches1andx/l islarge.Papanicolaou
M
Becausetheparticleevolutiondependsstronglyontemper- andList[12]haveshownthatR∝xinthejet-likelimitandRis
ature, the temperature distribution in the altitude chamber was constantintheplume-likelimit.Theyhavealsoshownthatflows
characterized; the temperature distribution depends on the con- with x/l <1 exhibit jet-like scaling and flows with x/l >5
M M
NASA/TM—2012-217257 4
TABLE2: Chamberconditions
Altitude Altitude DayType Temperature Pressure Density Chamber Nominal
Reynolds Chamber
Number Coflow
Velocity
(m) (ft) (K) (kPa) (kg/m3) (m/s)
6,100 20,000 Standard 249 46.601 0.653 17,900 0.7
7,620 25,000 Hot 259 37.650 0.490 18,700 1.0
9,140 30,000 Standard 228 30.149 0.459 25,800 1.4
12,190 40,000 Standard 217 18.823 0.303 32,100 2.5
exhibitplume-likescaling. [16]. Furthermore, momentum-dominated jets are self-similar,
For the measurements reported here, the axial locations of so a conserved scalar normalized by its centerline value is a
interest range from several nozzle diameters to 71 cm down- function of the radius normalized by the jet width, δ; that is,
streamofthenozzleexit. Inthisregion,Rissmallandx/l (cid:28)1 θ/θ = f(r/δ). For both momentum-dominated and buoyant
M CL
(see Table 1), so the effects of buoyancy should not be signifi- jets, δ is proportional to axial distance from the virtual origin;
(cid:16) (cid:17)
cant. A similar length scale analysis of the effects of the cold therefore, θ/θ = f(cid:48) r . Figures4a and 4b support this
nitrogen coflow [13] shows that the coflow effects should also CL x+xE
scaling: Figure4a is consistent with θ/θ =5.4(x+xE)−1 scal-
besmall. Therefore,theflowfieldismomentum-dominatedand 0 d∗
inguntiltheeffectofthealtitudechamberwallbecomesimpor-
shouldfollownonbuoyantjetscalinglaws.
tant at x+xE ≈130. Figure4b shows that θ/θ is a function
Formomentum-dominatedjets,itcanbeshown[14,15]that d∗ CL
ofr/(x+x )forr/(x+x )valuesthataresufficientlyfarfrom
a conserved scalar, such as the normalized temperature differ- E E
ence,θ ≡ T−T∞,isinverselyproportionaltothenormalizeddis- the chamber walls. (When interpreting Figure4b, note that the
T0−T∞ temperatureincreaseduetothechamberwallsismoreimportant
tancefromthevirtualorigin,(x+x )/d∗,wherexisthedistance
E onthepoorly-insulatedinstrumentplatesideofthechamber(+r)
fromthejetexit,x isthedistancefromthevirtualorigintothe
E (cid:113) thanontherelativelywell-insulatedwindowside(−r)andthatas
jet exit, and d∗ =d0 ρρ∞0. Diez & Dahm [11] 1 show that for theaxialdistanceincreasesther/(x+xE)valueatwhichthewall
a momentum-dominated or buoyant jet the distance x that the effects become important decreases.) Also shown in Figure4b
E
virtualoriginisupstreamofthenozzleexitisgivenby: are a curve fit to the data, the normalized concentration profile,
ζ/ζ ,usedbyDiez&Dahm[11],andthenormalizedvelocity
CL
xE =lMI25/2cI12δc3u,j(cid:34)(m0/(Jρ0∞/)ρ2∞()B50//2ρ∞)(cid:35)−12, (6) ptDoraomhfimloed,aenuld/tuhHCeuLsc,suuersirneednettbadylataHareuasonsfdeitnhtheeeftoparrmlo.fi[ξl1e7=s].ues−Teαhd(ebx+cyrxuert)hv2ee,wDfihtieeurzsee&ξd
isθ/θ ,ζ/ζ ,oru/u . Thewidthparameterα oftheθ/θ
where (7) CL CL CL CL
isbetweentheα valuesforζ/ζ andu/u ,furtherindicating
CL CL
I =0.262, (8)
1 thatthejetscalingisappropriateforthenormalizedtemperature
I2=0.131, (9) differenceθ.
c =0.36, and (10)
δ
c =7.2 (11)
u,j
4 InitialParticleEvolutionMeasurements
Inotherwords,θ =c (cid:0)x+xE(cid:1)−1,wherec isapproximately5.4 Particlemeasurementsweretakenbothinthetransitionpipe
θ d∗ θ
(seeFigure1)andinthealtitudechamberforburnercondition1
fromTable1andatallchamberconditionslistedinTable2. For
1Theformulagivenheredoesnotmatchtheonegivenbyequations42and47
in[11]. Thereseemtobeseveraltypographicalerrorsin[11],withthemissing theparticlemeasurementsmadeinthetransitionpipe,thesample
exponentof-1/2inequation47beingthemostimportant. Themissingexpo- wasdilutedwithnitrogenwithadilutionrationof1.91toprevent
nentcanbefoundbyfollowingthederivationdescribedinthetextof[11]and condensationandagglomerationinthesamplingline;thesample
substitutingequation46intoequation44.
NASA/TM—2012-217257 5
1.6 h = 6,100 m x = 0.71 m f/a = 0.045
L h = 6,100 m x = 0.91 m CL h = 9,140 m x = 0.91 m Curve fit
C θ
nce θ0.25 hh == 91,21,4109 0m m ff//aa == 00..000177 ce θ/ 1.4 hx == 01.23,01 9m0 m ff//aa == 00..000177 DHuieszs e&i nD eath aml
perature Differe00..2105 xxx === 000...367011 mmm ff5//.aa4x ==/d 00∗..003425 erature Differen 011...802 x = 0.61 m f/a = 0.032
m p
e m0.6
T0.10 e
zed ed T0.4
mali 0.05 aliz
Nor orm 0.2
N
0.00 0.0
0 20 40 60 80 100 120 1.0 0.5 0.0 0.5 1.0
Normalized Axial Distance (x+xE)/d∗ Normalized Radial Distance r/(x+xE)
FIGURE4: (a)NormalizedjetcenterlinetemperatureθCLasafunctionofnormalizedaxialdistance(x+xE)/d∗and(b)thenormalized
temperaturedistributionsasafunctionofthenormalizedradialdistance. Thesymbolcolorindicatesthealtitudeconditions,the’outer’
symbol indicates the axial position, and the ’inner’ symbol indicates the fuel-air ratio. Note that the effects of the chamber wall are
importantwhen(x+x )/d∗>130.
E
wasnotdilutedformeasurementsmadeinthealtitudechamber. Note, however, that the particle measurements taken in the
chambersuggestthatthecombustorparticleoutputisnotsteady
(seethenextsection). Thevariationofcombustorparticleoutput
4.1 BurnerMeasurements
with time is being measured, and for future tests, two particle
A representative particle number distribution in the transi-
measurement systems will be used so that the particle distribu-
tion pipe is shown in Figure5. Integrating the particle number
tions in the transition pipe and in the altitude chamber can be
distributiongivesatotalnumberconcentrationof1.2×107 par-
measuredsimultaneously.
ticlesperstandardcubiccentimeter,wherestandardpressureand
temperature are defined as 101.325 kPa and 298.15 K, respec-
tively.
FIGURE5: Particlenumberdistributioninthetransitionpipefor
burnercondition1(f/a=0.045)
NASA/TM—2012-217257 6