• NASA OonU'ammr _ No. 175080

AZA-C_-I75J30) CP_ICAL AND _CBE N86-16216

_ETE_MINATION C_ SCCT £OHL£NT_ATIONS IN A

MODEL GA-_ TURBINE COMBUS_Oh fin_l Report

_Uaited Tecnnologies _esearcz. Center) 99 p Unclas

HC AO5/MF AO| CSCL 2]_ G3/U7 03670

_ Soo Op_cal.co_ncedntratlons Pro.be Determination of in a Model Gas

, Turbine Combustor

W.A. Eckerle

T.J. Rosfjord

UNITED TECHNOLOGIES RESEARCH CENTER

East Hm'tfcrd, CT 0e108

January 1986

J

m/t 

Cle_il_, 0_;,-, 44135
\

NASA Contractor Report No. 175030

Optical and Probe Determination of

Soot Concentrations in a Model Gas

Turbine Combustor

W.A. Eckerle

T.J. Rosfjord

UNITED TECHNOLOGIES RESEARCH CENTER

East Hartford, CT 06108

January 1986

N/ A

National Aeronauhcs and

SDace Adm_,nfstral_or_

Lewls Research Center

Cleveland, Ohio 44135

,- III
ACKNOWLEDGEME NTS

Thls report covers the Investlgaflon performed by United Technologies

Research Center under NASA Contract NAS3-24223, The NASA program manager

was Mr, James Biaglow, The UTRC Principle Investigator was Dr. Thomas J,

Rosfjord; Dr. Wayne A, Eckerle conducted the experlmental effort and

assembled the test results. .4r, Sid Russell carrled on the fuel spray

character Izatlon ef fort whlle 14r, Roy Pel mas pray Ide guidance throughout

the test program, Ms, Janlce Fournler devoted many appreciated hours to

data management and Mr. Raplh Alello_s conscientious labors were largely

responsible for the timely execu, lon of the test effort.
_e_._-I-i  ̧ ̧_-,--_-

R85-956760-21

Optical and Probe Determlnatlon of Soot Concentration_

In a Model Gas Turbine Combustor

Table of Contents

Llst of Figures

L Ist of Tab Ies

Llst of Symbols

Summary

Section I - Introductlon

Section II - Fuel Chemical and Spray Properties

Fuel Analysis

Fuel Spray Characterlzation

Section III - Combustor, Test t aclllty, and Instrumentation

Combustor Description

Test Facillty

Instrumentatlon

Section IV - Test Conditions, Procedures, Data Acquisition and

Reduction

Test Conditions and Procedures

Data Acqulsltlon and Reduction

io

IV

VI

VII

VII

9

9

10

14

2O

20

23
Section V - Results

Particulate Concentration and SmokeNumber

Particulate Size and NumberDensity

Section Vl - Conclusions end Recommendations.

References

Tab I es

Figures

25

25

31

35

37
LIST OFFIGURES

I. Comparisonof Total Aroc,a_Ic Content for TwoAnalysls Techniques

2. Comparisonof NapthaleneContent for T_o Analysis Techniques

3. Fuel Spray Characterization Faclllty

4. Influence of Fuel Flow on Jet A Spray SMDfor Several Nozzle Sizes

5. Injector Size Required to Achieve Atomlzatlon Level

6. Generic GasTurblne Combustor

7. Fuel Nozzle and Air Swlrler

8. Primary Airflow Spllt In Generic Combustor

9. Avlatlon - Fuel Property Effect's Test Faclllty

10. Air Supply Systemfor Test Rig

11. CombustorConfiguration for Soot Sampling

12. Test Rlg Support Systemsand Instrumentation

13. Scattered-Light Ratio Dependenceon Particle Diameter

14. Layout of Particle Sizing Apparatus

15. Light Scattering Particle Slzlng Diagnostic

16. Optical Setcp for Visable Transmlsslon/Radlance_asurements

17. CombustorExhaust SamplingProbe Tip

18. Soot Loading for Jet A Fuel

19. Soot Loadlng for ERBSFuel

20. Soot Loadlng for ERBLS-2Fuel

21. Soot Loading for XTBFuel

22. Local Centerlir, e Fuel-Air Ratio Basedon GasEmission Measurement

23. Emlsslvlty at CombustionExlt

24. Radiation at Co-buster Exit

25. Fuel Effects on Particulate Concentration

26. Effect of CombustorPressure on Partlculate Concentration

27. SAESmokeNumberfor Jet A Fuel

28. SAESmokeNumberfor ERBSFuel

29. SAESmokeNumberfor ERBLS-2 Fuel

30. SAE Smoke Number for XTB Fuel

31. Fuel Effects on SAE Smoke Number

32. Effects of Combustor Pressure on SAE Smoke Number

33. Relationship Between Partlculate Concentratlon and SAE Smoke Number

iv
_4.

35.

36

37

38.

39.

40.

41.

Number Denslty for Jet A Fuel

Number Density for ERBS Fuel

Number Density for ERBLS-2 Fuel

Number Density for XTB Fuel

Effect of Fuel on Number Density

Average Pertlcle Dlameter at Combustor Exit

Relationship Between Partlculate Concentration end Particulate Volume

Particulate Density at Combustor Exit

V
LIST OF TABLES

I. Fuel Analysis Methods

2. Fuel Analyses

3. Nozzle Characterization

4. Combustor Open Area Distribution

5. Llner Effective Area Distribution

6. Alrflow and Fuelflow Conditions

v_
LIST OF SYMBOLS

CDA

D

f/a

I

I

0

I

L

n

N

NN

P

PC

PV

R

R2

SMD

SN)

C

SN

T

x

T

Effective Area of Liner Hole

Soot particulate characterlstlc dlemeter

Fuel-air ratlo

Scattered llght Intensity

Incident ilght intensity at sample volume

Axlal distance along combustor

Length of slx-louver combustor

Complex refractive Index

Soot particulate number density

Fuel Injector nozzle number

Local pressure

Soot particulate concentration, mg/sm 3

Soot particulate volume, sm 3

Measured radlance from soot particulates

Square of regression correlation

Fuel spray Sauter Mean Dlemeter

Crltlcal SMD

SAE smoke number

Local temperature

Light scattering size parameter

Llght scatterlng angle

Wavelength of scattered light

C_,plex _Ight scattering function

VlJ
SUMMARY

Contemporary gas turbine engines must be deslgned to meet both severe

efficiency and fuel consumption requirements as well as advanced durabilli_/

t_rgets. These constraints are not easily satlsfled at the same time. A

compromise among these confllctlng requirements Is not easily developed

during the design process because of a dearth of experimental data

regardlng certain aspects of the engine processes. One component that is

particularly difficult to design is the combustor liner. An optimum

combination of liner strenglh and liner coolant flow must be chosen so that

the liner can withstand the high radiative loads generated by soot produced

in the combustion process. Minimal liner weight and coolant flow rates are

sought to achieve fuel consumption goals. Proper design of the liner,

then, requires knowledge of the soot loading throughout the combustor. The

program goal was to address this problem by tracking the varlation in soot

loading along the centerl ine of a generic gas turbine combustor.

Soot Ioadlng was measured Inside a 12.7-cm diameter,

six-sheet-metal-louver burner. A single pressure-alomlzlng Injector and

alr swlrler were centrally mounted within the burner'_ conical dome.

Determlnatlon of soot loading along the burner length was achieved by

acquiring measurements first at the exlt of the full-length combustor and

then at upstream stations by sequential r_noval of liner louvers to shorten

the burner length. Alteration of the flcw field approaching and within the

shortened burners was minimized by maintaining a constant llner pressure

drop achleved by bypasslng flow that would have passed through removed

louvers. In this manner, data were acquired at six combustoc statlons.

Two test phases were conducted. First, fuel effects tests were

performed during which data were acquired with four test fuels. Fuel

physical properties were de-emphasized by using fuel Injectors which

produced highly atomlzed, and hence, rapldly vaporlzlng sprays. The burner

viii
exhaust flow was sampled at the burner centerllne to determine soot mass

concentration and smoke number. The characterlstlc particle size and

number denslty of the centerllne exhaust soot were determined by an optical

technique which interpreted scattered Ilght slgnals according to Mie

theroy. Optical technlques were also used to measure the transmlsslvlty of

the exhaust flow as well as the local radiation from lumlnous soot

partlcles in the exhaust. All data durlng this phase were acquired at a

slngle airflow condltion which simulated high-power operation of a gas

turbine combustor, namely, combustor pressure = 1.3 MPa and Inlet

temperature = 70OK. Test fuels were combusted at three fuel-air ratios,

which were specified to achieved nomlnal exit temperatures of 1240K, 1340K,

and 1_70K.

The second test phase involved acqu!rl_g similar data at a reduced

combustor pressure of 0.8 MPa. Airflows were flow-parameter scaled to

maintain the same approach-flow Mach number at reduced pressure. Data were

acquired at three burner lengths with two test fuels. The combustor

approach flow was again maintained independent of combustor length by

bypasslng excess flow "o retain constant llner pressure loss. The two test

fuels were combusted at the same fuel-air ratios Indicated above.

F

The particulate concenTratlon data indicated a strong soot oxl_ation

mechanism in the combustor secondary zone. Concentration measurements wlth

three louvers removed were at least an order of magnitude higher than those

measured for the furl-length combustor. Samples collected wlth shorter

burners were influenced by the dllution jets of this combustor. The jets

effectively penetrated to the centerllne and locally diluted the centerline

region. Particulate samples representatlve of the average loading in the

combustor front end, then, were not acqulred vla the cenrerllne sampllng

technlque. Transm!sslvlty and radiation measurements, which were

path-length diagnostics, Indicated slgnlflcantly higher loading near the

primary zone. These optical data imply that mass loading In the v lclnlty

of the primary zone was even more than one order of magnltude greater than

Icadlng measured In the ful!-leng+h combustor exhaust. Secondary-zone

oxldatlon was also a strong function of the flow temperature. Although

increased levels of so_i were produced at higher fuel-air ratlos, hlgher

exit temperatures, associated wl_n higher fuel-alr ratio, enhanced soot

X!
oxldation se that full-length combustor exlt concentratlons were lower at

higher fuel-alr ratio. The Influence of fuel chemical properties on soot

production was directly related to the fuel smoke point, where fuels with

the highest smoke point demonstrated less propensity to soot. Partlculate

concentratlons measured at reduced pressure Indicated less soot production

at the lower pressure. The data also Indicate that lower secondary-zone

oxidation rates may be associated wlth reduced combustor pressure.

Particulate number denslty and SAE smoke number, which were also

centerlIne measurements, displayed the prevlously noted trends. A good

correlation was obtained between particulate concentration and smoke

number. This agreement is attributed to the relatively small size

distribution of the partlculates, whose measured characteristic diameter

varied fro_ 0.25 /_m Inside the burner to 0.20 #Lm at The burner exit.

Particulate number density and characteristic diameter were used to

calculate particulate volume, which correlated with particulate

concentration. Particulate density, calculated from particulate

concentration and particulate volume, was nominally 20 percent that of pure

carbon. This low value for density corroborates the concept that soot

partlclulates are chaln-llke structures composed of tiny partlcles of pure

carbon.
I

Optical and Probe Determlnatlon of Soot Concentrations

Model Gas Turbine Combustor

SECTION I - INTRODUCTION

Substantial levels of soot are present within gas turbine combustors.

High production rates occur In the dome reglon where zones of high fuel

concentration exlst. Coupled with the high temperature In this prlmary

zone, such high soot levels produce intense radlatlve loads on the

combustor liner, elevating its _o_perature and thereby reducing the time to

failure. The level of soot produced is not known. A large fraction of It

Is oxidized In the secondary and tertiary zones of the combustor, producing

soot levels which, by not being visible in the exhaust stream, are

considered acceptable. The actual varlatlon of soot loading within the gas

turbine combustor has not been documented. Such data could be used to

define the Influence of chemical properties on primary zone soot

production, and the effectiveness of the combustor oxidation mechanlsms at

reducing the soot loading upstream of the exlt. Additionally, measured

changes In soot particle size and number density along the combustor length

would ald understanding of basic soot formatlon, growth, and oxidation

mechanisms.

A previous NASA progra_ (Ref. I) documented that fuel chemical

properties can Influence the radiative load on the combustor llner by

altering soot concentration in the primary zone. In that program,

well-controllee combustor tests were performed with 25 test fuels. Data

Indicated that the primary Influence of changing fuel chemical properties

was to alter soot produced In the combustor. That is, fuels whlch

displayed a high propensity to soot (l.e., low fuel speclflcatlon smoke

point) produced high radiative heat loads and exhaust soot concentrations.

As a consequence, high llner temperatures and exhaust smoke numbers were

_Iso attained. While the exhaust soot concentratlons were documented In

that prngram, no measurements were made w lthln the burner.
Thework reported here represents a ¢ontlnuatlon of the above work.

Thls program was directed toward documenting the soot loadlng In a gas

turbine combustor. Optical and probing techniques determlned

characteristic size and number density of soot aggregates, soot mass

concentration, and SAE smoke number along the centerllne of a generlc

combustor. Optical techniques were also used to measure the tram lsslvlty

and radiance of the exhaust flow. Data were acquired from tests using four

fuels with a slgnlflcant variation In chemical properties. Tests were

performed at two combustor pressures to document the Influence of this

varlable. Fuel spray characterlzailon studies supplemented the combustion

tests.

This document reports results of this program. Section II aescrlbes

the chemical analysis of the four test fuels along wlth the fuel spray

characterization effort to determine appropriate fuel Injectors. Sections

III and IV describe the combustor, test facility and Instrumentatlon, and

the test conditions, procedures, and data handling, respectively. Results

of the combustion tests are presented and dlscusse_ In Section V.

Conclusions and recommendations are listed In Section VI.

2
SECTIONII - FUELCHEMICALANDSPRAYPROPERTIES

Ir order to determine the effect of fuel chemical propertles on soot

loading within a combustor, tests were conducted wlth four fuels which

offered a s;gnlflcant range in chemlcal properties. The four fuels used In

these tests were Jet A, ERBS (Experlmental Referee Broad Specl flcatlon),

ERBLS-2 (e 60/40 (vol) blend of ERBS and BLS (blendlng stock)), and XTB

(Xylene Tower Bottoms). Jet A, which Is a hlgh-qual Ity petroleum-derlved

fuel produced in accordance with ASTM and USAF specifications, Is commonly

used in gas turblne englnes. ERBS fuel evolved from a NASA-directed

workshop on alternative hydrocarbon fuels (Ref. 2). Unl Ike most fuel

speclflcations, which place upper limlts on certaln chemical properties, a

single level (and tolerance) of hydrogen content is specified for ERBS.

Th;s approach minimizes tr_e chemical property varlatlon of subsequent

batches of ERBS production. ERBS has become a standard fuel for

NASA-sponsored fuel-effects Investigations. XTE_ Is a speclelty product

conslstlng _f various single-rlng aromatic compounds (alkylbenzenes) and

has been used in other fuel effects tests. BLS Is a mixture of XT_ and a

gas oli that NASA had obtained to use for modlflcation of fuel properties,

and contains single-rlng and double-ring aromatic compounds. The Jet A and

×TB fuels were procured by UTRC while the ERBS _nd BLS fuels were provlded

by NASA. UTRC blended the ERF_LS-2 rue! In the following manner. The

volume fraction specifications were translated to mass fractlons. A

shipping scale was used to weigh the quant!ty of each component, which was

them pumped Into a 1000 liter mixing tank. The entlre batch of the blend

was mixed by pump lng out of one end of the tank and Into the other.

Circulation time was sufflclent to dlsplece ?he blend volume at least ten

times. The blended fuel was subsequently pumped from the mixing tank Into

drums.

3
Fuel Analysis

A samp e of each test fuel _as analyzed by Southwest Research

Institute in accordance with the properties and procedures indicated In

T_ble I. The results of these analyses are presented in Table 2. The

levels of total aromatics and naphthalenes presented for any fuel were

obtained from mass spectrometrlc analysis. All hydrocarbons contalned In

the aromatic fraction of the sample contributed to the "total aromatics"

level. The naphthalene compounds were assumed to include the acenaphlhene

(CnH2n_14) and acenaphthalene (CnH2n_16) hydrocarbons. Volume

fraction values for total aromatics were determined from the reported mass

fraction data and the following assigned specific gravity values:

Hydrocarbo_ Type Speclf Ic Gray Ity

normal-paraffins 0.75

cyclo-parafflns 0.81

elky!benzenes 0.87

Indans and tetrallns 1.00

indents 1.00

naphthalenes 1.00

trlcycllc aromatics 1.28

The type of hydrocarbon species In the fuel was Independently

determined from more than one analysis. The mass spectrometric analysis

(ASTM D2425) separaled the fuel Into twelve classes while the fluorescent

Indicator absorptlon (FIA, ASTM D1139) technique reported only on three

general classes (saturates, oleflns, total arcmatlcs). The FIA was

supplemented with the u!travlolet spectrophotometrlc technique (ASTM 1840)

to determlne naphthalene content. A comparlson of the total aromatics and

naphthalene contents obtained by the two techniques Is shown In Figs. I and

2, respectively. The mass spectrometry and FIA results for aromatlcs agree

well conslderlr, g the wlde range covered a_d the general acknowledgement

that the FIA technique can be Inaccurate for high aromatlc levels. The

agreement between naphthalene analyses was not as good for ERBS & ERBLS-2

4
fuels. This result Is not surprls;ng as the UVtechnlque Is strictly

appllcable to f_els contelnl_g only up to 5 percent naphthalene. Both EP_S

& ERBLS-2 contain conslderably higher levels of naphthalene.

Fuel Spray Characterization

Varletlons in either chemlcal or physical properties could Influence

the burner characteristics. Fuel chemical propertles could prlmarlly

effect the !ype and concentration of hydrocarbon species wlthln the burner.

For example, hydrogen-deflclent fuels mlght produce greeter carbon

concen¢ratlons, resulting In higher radlatlon heat loads (and subsequently

higher liner temperatures). Fuel physlcal properties would primarily

effect the level of eeomization. That Is, fuels wlth disadvantageous

physical properties -- high levels of viscosity or surface tenslon -- would

tend to form coarse sprays, with these relatively larger droplets

penetrating deeper into the airflow end survlvlng for slgnlflcantly longer

time periods. Clearly the slze, location and Fntensity of the combustion

zone would respond to such fue_ dlstrlbutlon alterations, and consequently

_he combustor characteristics would also change. In order to isolate

chemical property l_fluences, the processes dependent on physical

properties must be mlnlmlzed. Only by achieving nighly-etomlzed and hence

raplaly-vaporlzing sprays can this goal be setlsfled.

In principle the finest level of atomization possible should be used

to truly mlmlmlze the Influence of fuel physlcel propertles on combustlon

efflclency. This extreme however, would have Imposed unacceptabl demands

cn the test program.,-- excessive fuel pressures and/or nozzle substltutlon

for every fuel, for each fuel flow rate, would have been required. An

atom!zat,on goa! that would acceplably mlnlmlze the Influence of fuel

physlcal properties was seugnl.

The analytical technique of Belial end Lefebvre (Ref. 3) can be used

to analyze fuel sprays char_cterlzed by a Seuter Mean DlBmeter (S.MD). In

partlculer, this analysis Includes system charac.terlstics that deflne

reactlor_controlled an_ vaDorlzet!on-controlled operation. Convectlve heat

en_ mess transfer Is Included by assumlng that the droplets do not respond
to the turbulent velocity fluctuations of the airflow. A critical SMD can

be Identifled (SMD) wlth the analysis. That is, for SMD < Sl_]c, fuel c

vaporization would nit control heat release and, hence, combustlon

efflcTency.

The critical aroplet slze to avoid vaporlzation control In the

combustor used in this experiment was defined prevlously (Ref. I). In

particular, SMD c values were sought that assured rapld vaporization

within the combustor primary zone which, based upon the test condltlons and

flow splits, had a resldence tlme of approxlmately 5 ms. Ca lculatlons

indicated that for Jet A fuel, a 20 percent turbulence Intenslty, and a

droplet lifetime half the primary zone residence time, SMD = 52_m.

c

That Is, a Jet A spray with an SMD < 52 _m would vaporize sufflclently fast

so as not to limit the heat release r_te. The least volatile fuel that was

tested hat distillation characterlstlcs similar to a No. 2 oli. For the

same cond!tions as described above, the crltical diameter was calc_:lated to

be SMI]c = 45 _m. Based or these results a sl Ightly conservative spray

atomization goal of ;_._ = 40 _ 5 _m was defined for the te_t fuuls at the

medren fuel f!owrate assoclated with the condition havlno a fuel/alr ratlo

(f/a) of 0.018.

The four test fuels In this exper!,ne_ts d'cl not exhibit a wlde range

In physical properties. For example, data acqulred previously (Ref. I)

wlth a single fuel Injector Indicate a rel_tlvely small span of atomization

qual Ity:

Jet A 39

Xl'B 52

ERBS 47

Medlan

46.5

However, combustion tests were to De performed both at the hlgh-power

condltlon achieved In the prevlous program (combustor pressure = 1.3 MPa)
as well as at reduced pressure levels. In order to assure meetlng the

atomlzation goal at reducedpressure, an Injector characterization Study

wasperformed to guide selection of Injectors that would achieve the

deslred high levels of spray atomization at two reduced pressure levels of

0.8 MPa and 0.3 MPa. For the same combustor Inlet temperature (70(2)I<),

airflow and fuel flow rates of 61.5 pct and 23.1 pc+ of the high power

rates correspond to the I_o reduced pressure conditions, respectively.

Characterization of the fuel sprays was performed In the UTRC Ambient

Pressure Fueg Spray Faclllty located In the Jet Burner Test Stand (JBTS).

The pertinent components used In the present study are shown In Fig. 3.

Fuel Injectors were mounted In the faclllty and connected to the fuel

dellvery system. Jet A fuel was dellvered to the injectors from an

underground storage tank and metered vla a turbine meter. Fuel pressure

and temperature were measured at the injector. Fuel spray pattern and

droplet distribution were documented as follows. A high power General

Radio Strobolume lllumlnated the spray with a toms light pulse,

s,_bstant!aliy freezing the droplet motion. (Photographic records of the

spray were obtained on Polarold film to determine the Included cone angle).

Droplet size dlstrlbutlon was measured In a plane 5.4 cm downstream from

the injector with a Malvern Model ST1800 Particle Size Anaiyzer. This

Instrument is based on Fraunhofer diffraction of a parallel beam of

monochroma+ic light by moving or statlonary particles. A He-Ne laser beam

traversed the spray diameter and the dlffracted llght was sensed on a

30_element photoelectric detector. The data were acquired using a 300-mm

focal length collecting lens which permltted detection of droplet sizes

be#wean 6 and 560 _m. The photocells were scanned 200 times (approximately

2.6 sac) to acquire a statistlcally meaningful average for each data polnt.

A dedicated mlni-computer stored the diffracted light data and, upon

request, executed an analytical program to Interpret these signals in terms

of a Rosin-Rammler droplet ¢Istrlbutlon and to calculate a spray SMD.

Simplex pressure atom lzlng injectors produced by Hago M_nufacturlng,

Inc. were used in these tests. All Injectors produced hollow cone sprays

with a rated Included cone angle of 80 deg. Elght Injectors, 10entlfled by

nozzle c J,_ber (NN, the volume flow _GPH) dellvere_ at a pressure drop of

I00 psl_), were Investigated. Two Injectors (NN_35. arld 32) were In a
range suitable for the high-power condition and three each were for the 0.8

MPacondition (NN=18,20, and 22) and 0.3 MPacondltior (NN=8,9, and 10)o

Three fuel flowrates were investigated for each nozzle, representlng the

rate assoclated with fuel-alr ratlos of 0.015, 0.018, and 0.022 for each

condition.

The data acquired In tests with the elght nozzles are presented In

Table 3 and Fig. 4. Over the flow range Investigated, SNID varled linearly

wlth fuel flow, a trend consistent with data oDtalned previously (Ref. I),

but In confllct wlth the weaker relatlonshlp predlcted by standard

atom lzation correlations. In the prlor study, It was concluded that

surface tenslon forces, as represented by the nozzle exit Weber number,

could slgnlflcantly Influence the atomization processes, it was

demonstrated that for the very low fuel flows often used In developing the

atom lzat!on correlations, this Influence was not Important while for larger

(practlcal) flows, the Influe._ce was dominant. These recent date appear to

again reflect th;s influence.

As prevlcusly indicated, the spray produced by the four test fuels Is

similar'. Hence, for a given pressure condltion, a single nozzle could be

used to achieve acceptably flne atomization of the four test fuels. Wl-h

an atcrnlzatlon goal of SMD = 40 ± 5 Nm at the test condltio_ corresponding

to f/a = 0.018, the trends presented In Fig. 4 were used to determlne a

fuelflow - nozzle number reiatlonship at constant SND (Fig. 5). The flow

rates of Jet A associated with the medl_n f/a at each of the three

combustor pressure levels ere Indicated. Since the mean atomization level

for the four _uels (presented prevlously) was 19 pct greeter than the Jet A

value, nozzles which produce Jet A sprays wlth SMD=34 _m should satisfy the

atomlzation goal for all fuels. Nozzles with NN = 30, 18, and 7 should

produce the deslred atomlzation levels at the three pressure condltlons.

6
SECTIONIII - COMBUSTOR, TESTFACILITY,AND INSTRUMENTATION

This section of the report describes both the burner, speclflylng Its

geometry and performance, and the specialized test facility assembled for

these efforts. A detailed descrlptlon of the Instrumentation Is also

included.

Combustor Description

The test combustor was nearly Identlcal to the one used previously

(Ref. I). Th;s combustor embodied the features of a gas turbine burner.

That is, the burner was a high heat release devlce, with strong

swlrllng-re<ircu;ating flow structure at the front end (l.e., primary zone)

fcllowec by penetrating jets of air to gredual_y reduce the local fuel-alr

ratio, and hence gas temperature, to levels acceptable to a turbine.

A photograph of the combustor iS In Fig. 6. The cylindrical burner

was louver-cooled with an inside diameter of 12.7 cm and a length of 41.1

cm. The ca, buster consisted of a dome, constructed from a frustrum of a

90-dog cone, and six conventlonai sheet-metal louvers. The dome cooling

air was admitted through four rows of equally-spaced holes. Each louver

was fed by a ring of equally-spaced holes wlth four of the louvers

conteinlng six larger holes to odmlt combustlon alr TO the burner. These

combustion alr holes represented the greatest devlatlon frcsn axlsynvnetry.

The number end diameter of a!l combustor holes are listed In Table 4. Thls

burner was cre_ted by modifying the hole pattern In a JTI2 combustor to

permit operation over a greater range of test condltlons. That is, the

original JT12 was rated for a combustor exlt temperature up to 1145K.

Alteration of the hole pattern to Increase coolant flow permits routlne _se

tc exit temperatures up to 1480K.

A flange on the combustor dome was provided to centrally mount a fuel

Injector-swTrler combinatlon. As previously Identlfled, pressure otomlzlng
Injectors produced by Hago Manufacturing, Inc. were used (Fig. 7a). Aii

Injectors produced hollow cone sprays w!th _ rated Included cone angle of

80 deg. Nozzle sizes were determined from spray characterization data

described In Section II. The elr swlrler, which encircled the fuel nozzle,

provided the swirl necessary to assure stable combusto,- operation. The

swlrler enhanced fuel-air mixing and distribution as well as establ Ished

the reclrculatlng primary zone flowfleld. The swlrler was a commerclally

available device developed by Pratt and Whitney Aircraft for the JT12

combustor (Fig. 7b). An annular clamp rlng assured proper posltlonlng and

seallng of the injecfor-swlrler combination to the combustor flange.

The alrflow pattern In this burner was well documented In callbratlon

tests (Ref. I). First, a CO 2 tracer was used to determine the amounts of

aTrflow from all sources which partlclpated In the primary zone. Data from

these lasts Indlcated that 19.5 percent of the total air flow partlc_pated

In the primary zone flowfleld (Fig. 8). Hence, the primary zone

equivalence ratio Is 5.1 times the overall equivalence ratio. Second,

callbration tests were performe_ to deflne the combustor airflow

dlstrlbutlon over The entire burner length. The effectlve area of liner

holes at each axial station (l.e., dome, louver cooling, combustlon alr

holes) was determined as Indlcated In Table 5. The airflow swlrler was

calbirated In a separate test. The second column of Table 5 Indlcates the

cumulative llner alrflow. When used wlth a fuel Injection rate this

airflow schedule permits calculatlon of the global equivalence ratio at

these combustor axial positions.

This burner operated quite stably In previous tests. Combustion

efflclency was always greater than 99.9 percent, the nominal combustor exlt

pattern factor was 0.13, and the nominal liner pressure drop was 2 percent.

By malntalning the 2 percent llner pressure drop, combustor operation of

the shortened burners In this progr_ was also stable.

Test Facility

The experlmentel test program was conducted In the JBTS, which Is

seif-contelned faclllly with four test cells equipped rot hlgh-pressure

combustion tests. The JBTS provldes test cells with control rooms,

I0
assemblyareas, automatic data acquisition systems, and alr, fuel, and

gaseous nltrogen supply syst_.s.

The test program primarlly used hardware resldual to the previous NASA

program (Ref. I), wlth some components fabricated for the needs of thls

program. The test facillty consisted of three sections: an air

preparation section, a test and Instrumentation section, and an exhaust

section (Fig. 9).

Air was supplied to the air preparation section through the system

depicted In Fig. 10. Two multl-staged reciprocating compressors, capable

of pumplng a combined flowrate of up to 4.5 kg/s, provl_ed air at pressures

up to 2.7 MPa. The airflow for the com.bustlon tests was heated by an

Indlrect-oll-flred burner prior to entering the air preparatlon sectlon;

the typical preheat level was a 420K. The heated alrflow was regulated In

the _est cell and metered by a venturl, wlth appropriate measurements of

elf pressure and temperature performed upstream and at the throat of this

device. The temperature of the venturl body was also measured to account

for thermal expansion of the throat diameter. The metered airflow was

heated further by use of en electrlcal resistance-type heater. A plenum at

the heater exit assured that uniform airflow veloclty and temperature

proflles were delivered to the test scction.

The test section consisted of spacer spool sections, a combustor

housing, and instrumentation rings. The spacer spools provided necessary

access to remove the combustor housing. They also provlded support for

arrays of four total pressure probes and four thermocouples to document the

airflow approaching the burner, and bosses to route out liner thermocouples

and pressure IInes.

The combustor housing (Fig. 11) was a simple spool section fabricated

from commerlcally-avaIlable pipe with an Inside diameter of 15.2 cn,. A 1.3

cm annular gap be+ween the liner and housing provided adequate backside

convective cooling of the burner louvers. The housing contained a single

boss to route fuel to the fuel nozzle. Fittings near the downstream end

permitted Insertion of pltot-static probes to measure the liner pressure

loss and a bleed port to adjust the pressure loss.

ll

e-- o
The combustor attached to a mounting rlng vla a small flange attached

to the l lner at the burner exit (Fig. 11). Burner al Ignment was aided by

centering _abs mounted on the dome. The fuel llne, which was flexible to

accommodate the i lner thermal growth, consisted of two sections. An axial

length incorporated two concentrlc tubes w lth fuel dellvered through the

inner tube and the outer tube providing an !nsulatlng alr gap. A radial

length included a steel brald/teflon tube flexible llne, wrapped by a hal Ix

of copper tube to provide a water-cooled heat shleld. In order to make

measurements Inside _he burner, shortened combustors were produced by

removing the complete downstream-most louver and welding a repl_cement

flange at the new exlt pla;,e. Replacr,ent lengths of the concentric tube

fuel line enabled fuel to b_ del Ivered to the shorter burners. Slnce the

shortened liners provided a reduced effective open area (CDA), less burner

airf!ow was required for constant l l;_er pressure drop. Reducing combustor

airflow to match the decreased CDA, however, would have alterred the

approaching flowflel¢, affecting both the penetration of jets through the

llner and the internal flowfleld. To el Imlnate this influence, the

combustor total a!rflow (i.e., alrflow approaching the burner) was held

cons?ant, with airflow greater than tha + required to matcf the full-length

combus_ pressure loss bypassed through oriflce plates mounted In the

annular region at the combustor exit (Fig. 11). Each plate contained

equally-spaced holes sized to compensate for the decreased liner open area

of shortened burners. Hole sizing was based on the callbratlon results

obtalned previously (Table 5). Liner pressure drop was determ;ned from

pltot-static tubes placed In the annulus between the liner and housing and

static tapes Instal led In the combustor dome. A remotely adjustable byDass

bleed was available to fine tune the tota_ bypass to mchieve desired llner

pressure drop.

This technique of shortening the liner to make measurements Ins!de the

burner Incurred signlflcantly reduced cost relative to designing and

fabrlcating elaborate combustor housTngs that would have allowed optical

and probe dlagnostlcs to transverse parallel to the combustor centerllne.

]hat Is, Instead of mcvlng the diagnostics t_erd the fuel nozzle, the fuel

nozzle was moved toward the dlagnostlcs, which remained flxed. By

exerclslng the Indlcated test procedures, the ilc_fleld bel_een the nozzle

12
a_d measurementplanes Is not bel leve_ to have beensignificantly altered

by removal of clow_streamlouvers.

Twoinstrumentation rings, deslgnedand fabricated previously (Ref.

I), were mountedto the combustorhouslng. Theserlngs were specially

constructed, flange-cooled units (Fig. 11). Theparticle sizing ring

provided optical access for scattered llght signals, The probe mounting

ring provlded fittings to mountup to three probes. In this program, a

slngle probe was utlilzed, with its sampllng orifice located on the rig centerllne.

The exhaust section consisted of an adapter followed by a water-cooled

T-sectlon and a backpressure value. The T-sectlon provided a 7.6 cm

diameter v lewport to permit direct observation of the combustor exit plane.

A remotely-opera tea butterfly valve was used to control the test-section

pressure. A high-pressure water quench reduced the gas temperature

upstream of the valve to tess than 700K to prevent damage to it.

The fuel cei Ivery system consisted of three subsystems: a startup

fuel subsystem, a test fuel subsystem and a nitrogen purge subsystem. Jet

A was suppl led to the test cell from underground storage tanks by posltlve

displacement pumps. This fuel, referred to as Jet A-U, was the startup

fuel used prior to switching over to the test fuel. Data were acqulred

wlth the com,,bustor operating on Jet A-U prior to operation on any test fuel

to verify conslstant combustor operation. Jet A-U had propertles nearly

Identical to the Jet A test fuel. Drum quantities of the test fuel were

del Ivered by the test fuel subsystem, wi_ich was capable of dellverlng 4.6

liter/ml_ at a pressure of 6 MPa. Two solenoid valves, one In each fuel

subsystem, were actuated by a common electrical circuit. A normally-open

valve In the Jet A-U system and normally-closed va!ve in the test fuel

system were switched In unison to provlde a rapid, posltlve change In fuel.

The nitrogen subsystem was available to purge _he fuel nozzle and del Ivory

llnes inside the combustor rlg and to cool these components clurlng the

setup of the test condition. The fuel system Is depicted as part of Fig.

12.

13
Instrumenta¢ion

The test facility was Instrumented as described below. The parameters

measured are Indicated in Fig. 12.

Measurements were made to document the airflow rate, pressure and

temperature approaching the model combustor. The airflow rate was

determined using e venturl wlth a 2.286-cm throat diameter; pressure and

temperature upstream and pressure at the venturl throat were measured. The

dlstrlbutlon of temperature and total pressure a+ the test sectlon inlet

were documented using arrays of four thermocouples and four total pressure

probes. The test-section housing contained two fittings, located 180 deg

apart near the downstream end of the housing (Fig. Ii), for mounting

pitot-statlc probes to document the total and static pressure of the

alrflow proceed!rig through the annulus. Several thermocouples Installed In

the adapter section indicated the combustor exhaust temperature.

The fuel supply contained provlslons for acquirlng pressure and

temperature measurements necessary to control the flow. Fuel flowrate was

measured wlth a turblne meter. A mass flowmeter was not required since the

viscosity variation among the test fuels was small. Adc voltage source,

interlocked with the fuel swltchover valves, produced a signal to identify

dale points acquired when operating with test fuel.

The combustor llner was Ir.strumented with thermocouples and Internal

pressure taps. Twelve type K thermocouples were attached along an axial

llne at one angular posltlon of the burner, with another six attached along

a line on the opposite side of It. In the _elve thermocouple array, two

were placed on each of the six louvers, wlth one thermocouple opposite the

edge of the Inner fllm slot lip and the second approxlmately 2.5 cm farther

downstream. The six thermocouple array contained one sensor on each louver

at the second axial posltlon. Two static pressure taps were attached to

the first louver to provlde a measurement of burner static pressure, which

was used to determine and monitor the llner pressure loss for the dlfferent

burner lengths. The twelve thermocouple array and one pressure line are

visible In the photograph contained In Fig. 6.

14
Soot particle size and concentratlon (numberdensity) were determlned

from the scattered l lgh÷ emanating from a 15 mm3 samplevolume located 7

cm downstreamof the combustorexit centerl Ine. The scattered-llght

slgnals were interpreted according to Mle theory of l lght scattering. This

technique has beendetailed by several authors (Refs. 4, 5, and 6) _ith a

critical assessmentof its accuracy given by Bonczyk (Ref. 7). In brief,

this theory pred!cts the intensity of light scattered 0y partlculates as a

function of the scattering particle properties, scattering geometry and the

incident Intensity:

I = K * I0 *N *_

where: I

I0 =

= light intensity scattereC by particles

constant including scattering solld angle

Incleent light Intens!ty

N = particulate number density

= complex scattering function

The scattering function,_, Is dependent upon the slze parameter, x,

the scattering angle, e, and the complex refractive Index, n:

= (x, 8 , n)

where:

x = TrD/T, D = particle dlameter

T = wavelength of scattered light

Is also responsive to the polarization of the light. Strlctly, thls

description !s accurate only for spherlcal particles of uniform size. The

extensions of the theory to permlt deflnltion of polydlsperslons result In

greater analytical and experimental complexlty. For combustlon

15
appllcaeions, where the particulate shape is non-spherical, i_ Is

difficult to determine a_l the parametersof the polydlsperslon.

Therefore, for such applications, It Is commonto assumea monopdisperse

particulate s!ze distribution. This approximation (and the accompanying

assumptionof spherical particles) limits the accuracy of slze and

concentration determinations.

The evaluation of particulate size and number density relied upon the

angular dlsymmetry of the scattered llght. From the above description, for

a fixed polarlzation of the light (chosen to be perpendlcular to the

scattering plane), the ratio of light Intensity at two different angles, el

and 82 Is:

I(81)II(82) = (D,81,n)/ (D,82, n)

This ratio Is a function of D alone for given values of the complex

refractive index and scattering angles. !n this program, values of 81 = 45

deg and 82 = 135 deg were used; the scattere_ ligh+ had a wavelength of

514.5 nm. The dependence of the ratio of scattered light on D is deplcted

In Flg. 13 for two values of n. Note that the theory permits size

determlnatlon for D < 0.3 _m; for larger diameters, the ratio Is

multivalued and unambiguous slze determination cannot be made. The

proper value for the complex Index of refraction of the combustor exhaust

particles was not known; the value l!kely depended on the chemical

composition of the particulates. The two values used to generate the

curves In Fig. 13 were obtained from measurements either on graphite or on

soot from an acei3,1ene flame. For the valid range of diameter

determination, the uncertainty Introduced by these two n values was not

great, however. The value for graphite (n = 1.94 - 0.661) was used In the

data reduction. Once D had been determined, the particulate number

density, N, was calculated fro_ the scattered light intensity measured at

81 and the known geometrll of the scattering setup.

The particle slzing apparatus assembled for thls program Is shown In

Figs. 14 and 19. The incldent light was produced by an argon-lon laser

with an output power level of approximately lw at a wavelength of 51_.5 nm.

16
The polarization of the output beamwas rotated to be perpendicular to the

scatterlng-plane. The beam,which was choppedat a frequency of 2008 Hz,

was directed through a recess sapphire windowand across the combustor

exhaust. Twoscattered light detector assembIleswere rigidly attached to

the test duct, one at 45 dog and one at 135 deg from forward scatterlng.

The fabrlcatlon tolerances of the assembly mountings were specified to

assure precise allgnment of them. During Installation of this apparatus it

was observed that beams from two He-Ne alignment lasers Intersected on

the test duct centerline. Each detector assembiy contained a sapphire

wlndow, a polarlzlng disk, a narrow-pass fllter (centered at 514.5 nm) and

a fast linear focused (EMI +ype 980/B) photomuitipl ler tube (PMT). The

sol Id angle of the scattered fight was deflned by two 3.1 mm dle appertures

(separated by a dlstance of 20.0 cm) located along the detector centerilne.

The output fror each PMT was Input to a Iock-ln amplifier which was

referenced to the chopper frequency. This setup enhanced the

signal-to-nolse ratio by providing an output voltage proportlonal to the

difference between the laser-stimulated scattere_ llght and any random

light which mlght have been detected.

The laser beam path also contained a focusing lens. Oombustor

shakedown tests conoucted without a lens In the previous program (Ref. I)

Indicated substantial beam dlameter growth at the aIlgnment window. That

Is, the 1.3-mm dl_eter laser beam had grown to fill the 12-mm dlam.eter

exlt port. This growth was attributed to "thermal bloc_nlng" which OCcurs

as light passes through gases which possess large temperature gradients.

The thermal gradlents produce gradlents _n the index of refraction which

result In a lens-llke expansion of the ray. it was suspected that the

bloomlng occurred In the window recesses where cool nitrogen purge flow and

hot combustion gases were unavoidably mixed. The lens fOCused the laser

beam on the test duct centerllne to mlnlmlze thls problem.

In addltion to the scattering dlagnostics, trans_Isslon measurements

of the laser source llght used for the scatterlng measurements were

analyzed. Thls setup Is deplcted In Flg. 16 whlch shows the placement of a

detector to sense the transmltted light. Date were acquired both wlth and

wlthout combustion to determlne the absorptlon of the laser beam as It

traversed the combu_tlng flow. In these measurements a neutral denslty

17
filter was used to reduce the slgnal level to wlthln detector llmlts. A

lock-!n ampllfler referenced the detector slgnal to the chopper located on

the laser slde of the test rlg. Radiance measurements were also made by

blocking the laser source and Inserflng a chopper In front of the detector

(Fig. 16); the filter was withdrawn to increase detector sensitivity. The

devices were driven by pneumatic cyilnders actuated from the control room.

The detector, sensitive only to visible and near IR radlatlon, sensed

radiation generated by the lumlnous soot particles only.

Combustor exhaust products were probed near the combustor exlt to

determine gaseous emlsslon levels, smoke emlsslon levels, and soot mass

loading. A sampllng probe was positioned to locate Its Inlet or lflce on

the rlg centerIlne approximately 8 mm downstream of the scattering sample

volume (Fig. 11). The probe had a 1.3-cm CD wlth a 3.7-mm sampllng port

(Fig. 17). The probe body was water-cooled to assure its survlval In the

hlgh heat load condltion created with shortened burners. The outside of

the sample tube In the probe was coated wlth 0.3-mm thick ceramic to reduce

heat exchange between the sample and coolant and, hence, _o avoid Ic_ local

sample temperatures that could promote condensetlon. Nitrogen diluent

coul_ be added to the sample near the probe lip to quench the oxldation

processes and reduc_ the sample dew point. The sample temperature measured

at the probe exlt was used to determine when nitrogen dilution was

required. If the sample temperature measured wlth the shortened burners

was significantly larger (more than 8OK) than thai measured wlth the

full-length burner, diluent was added to dolor soot cxldation in the

sampling system.

Particulate laden flows were extracted through the probe. The sample

was dlvlded and passed through two heat exchangers, as shown In Fig. 12,

before entering transfer llnes to pass out of the iest cell. Heat

exchangers were required to reduce the sample temperature below 400K in

order to ensure that the teflon coating over the transfer llne Interlor

dld not melt. Separate transfer llnes and sampling systems for the smoke

and soot measurements were determ lned to be necessary durlng shakedown

tests. R,e flowrates and sampllng tlmes to acqulre mass samples were much

greater than the flowrates prescrlbed by SAE ARP 1179 for measurlng smoke

number. The amount ol soot col:ect_d In •typTcal smoke sample was

18
calculated te be less than one percent of a typical soot mass sample.

During tests where both measurements were made with the same Tra_sfer iine,

SOOt, which tended to adhere to the transfer line walls, wouI_ randomly

break loose. This effect, which was a negligible perturbation on mass

samples obtained over extended s_mp!Ing periods at h!gh flowrates, had a

significant Influence on smoke number measuremenYs. Consequently, to

overcome the erratic smoke number results that were belng ecqulre_, a

separate transfer llne and fllter system was dedlcated to smoke number

sampllng. Repeatable smoke number measurements were gathered with the

dedlcated system.

During shakedown tests, soot samples were acqulred using four

different filters -- two paper fllters and two Fluoropore teflon fllters.

One of the paper fllters was Watman No. 4, the me_.brane speclfled for SAE

smoke number determination. This materiel had Insufficient filtration

efficiency as Indlcatea by slgnlflcant scoot stains that were collected on

the second of two stacked fllters. The other paper filter, Mllllpore HA,

had sufficient efficiency but suffered form the problem of all paper

filters -- it absorbed water form the atmosphere. Subsequent welghlngs of

new fllters Indlcated an increasing tare because of this tendency. Rather

than drying the paper fllters before and after sampilng to overcome the

water absorption problem, teflon membrane filters, which are hydrophoblc,

were Investigated. These filters, with a nom lnal pore slze of 0.5 m, have

demonstrated a filtration efflclenc, of greater than g9 percent for

particles down to 0.03 _m _Ref. 8). This performance arlses from, the

flbrous structure of the fllter which Is apparently formed from 0.2 _m

fibers. Both Mllllpore Type FA and FH fllters were Investlgated. The

former, which had a polyethylene backing, was unacceptable because the

backing melted In the heated fllter holder. The Type FH collected samples

efflclently and was used successf_lly throughout the program.

Though the concern of water absorption by the filters was eliminated

by using Seflon flltars, thc potentlal for water absorption by the

colleciad sac+ also needed tc be addressed. To determine whether water

absorptlon by the soot was a problem, several of the acqulred samples were

weighed Immedlately before and a_ter drying the samples In an oven. The

weights agreed to wlthln 10-2mcj Indlcetlng thee water absorptlon by the

soot was Inslgnlflcant.

19
SECTION IV- TEST CONDITIONS, PROCEDURES,

DATA ACQUISITION AND REDUCTION

Soot loading in the burner was documented In terms of three variables:

fuel chem lcal properties, fuel-air ratlo, and combustor pressure. Soot

loading was documented for slx dlfferent combustor lengths. This section

of the report detalls the test condltlons and procedures for settlng up and

conducting tests as well as for acqulrlng data.

Test Condltlons and Procedures

Two phases of combustor tests were performed: fuel-effects tests and

pressure-effects tests. The fuel-effects tests determlned the Influence of

fuel chemical properties on soot loadlng. A single alrflow condition,

slmulating high-power operatlon of a gas turbine englne, was used for the

fuel effects tests. The approach airflow pressure, temperature and

flowrate for this condition, deslgnated Test Condition I in Table 6, were

Identical to those used previously (Ref. I). These parameters were

Independent of combustor length. Bypass flow, set by the open area In the

mountlng ring, was adjusted to achieve a relatively constant liner pressure

drop for all burner lengths. Soot loading was documented for four test

fuels: Jet A, ERBS, ERBLS-2, and XTB. Each fuel was tested at three

flowrates that produced full-length combustor Ideal exhaust temperatures of

approximately 1240K, 1340K, and 1470K. These three temperatures were the

Ideal t_mperature levels assoclated wlth combu_tlng Jet A at fuel-alr

ratios of 0.015, 0.018, and 0.022, respectively. The flowrates for the

other three fuels required to achleve the same exit te_peratures were

sllghtly different. Requlred flowrates for each fuel were determined from.

thermochemlcal calculations using chemical propertles Identlfled by the

fuel analysis. A Ilstlng of these fuel-alr ratios Is contained In Table 6.

Tests were performed at a reduced combustor pressuring of 0.8 MPa to

document the Influence of combustor pressure on soot loading. The same

Inlet temperature of 700_ was used wlth the mass flow decreased In

2O
' " Ion i denoted as Test ConditJon 2 In

Table 6. The ccmbustor approach flow was again Independent of burner

length, wlth excess alr bypassed to retain constant liner pressure loss fop

each of the three burner lengths investigated at reduced pressure. Two

fuels, Jet A and ERBLS-2, were combusted at reduced pressure with each

Injected at flowrates required to achleve the same full-combustor Ideal

exit temperatures noted above.

Shakedown tests were conducted to Initially check out combustor

operation and Instrumentation systems. Also durlng these tests, sampling

times (nom lnelly 10 min.) and flo, rates (nominally 0.08.? sm3/mln) were

established to gather a satisfactory sample for the mass ccncentratlon

measurements. A minimum of I mg of sample was sought so that the sample

weight could accurately be discerned from the nc_inal 50 mg fare weights

of the teflon filters. As sect loading Increased wlth shortened burners,

these sampling times, which were the primary determlna_t of test duration,

were reduced to mlnl_ize fuel usage.

Startup procedures were standard for each test day. The data

acquisition system was set up wlth pressur_ tranducer and thermocouple

references checked, flowmeter and analyzer outputs zeroed, and signal

empllflers call_rated. If optical data were to be acquired, the laser was

allgned and all mirror, window, and fllter surfaces were cleaned.

Appropriate JBTS support systems were activated and purge floxs were

establlshed through the sample probes, ducts providlng optical access, and

fuel delivery llne. Airflow from the 2.7 MPa facl!Ity system was Initiated

and heated by both indlrect-flred and electrical heaters. After alr

temperature Increased to dpproximately 730K, the backpre_sure value was

closed to ralse the pressure to approxlmately I MPa. The fuel purge was

then terminated and Jet A fuel, supplled fr_. a large underground tank at

the JETS, was slowly introduced. (Thls fuel Is t_rmed Jet A-U). At these

conditions, the fuel Ignited spontaneously at a mlnlmal fl_, avoldlng a

Sudden Increase In burner pressure. The fuel flowrate was Increased and

the alrflow Parameters (pressure, temperature, flo, rate) were adjusted to

deslred setpolnts. Probe purge flc_s were terminated and the exhaust gas

temperatures observed to conflrm stable steady-state conditions had been established.

Zl
Performanceat each burner length were initially Investigated with Jet

A-U. Detalled data, including pressures, temperatures, soot samples, smoke

samples, and gas emission analysis for selected burner lengths, were

acquired at Test Condition I for all three fuel-air ratlos. The data were

acquired to documentthe burner performanceas weil as to establlsh a small

data base for referenclng the combustor operation.

Measurements wlth the test fuels were Initiated by acquiring data wlth

Jet A-U at a f/a = 0.018. Comparison of these data wlth the Initial Gate

set aided In verifying that the burner performance remalne_ constant. The

fuel supply wad lhen _wltched to operation on a test fuel. Swltchover was

accompllshed by the simultaneous activation of solenoid values which

provided for an uninterrupted flow of fuel sc _hat the burner never

extinguished. The test fuel was fed fro_ two drums, each contalnlng

approximately 190 liters of fuel, to provide enough fuel to achieve the

relative long test time required to acquire soo_ samples. Upon completion

of raeas_rements with the test fuei, the fuel supply was switched back to

Jet A-U in a similar manner. Data were again gathered at f/a = 0.018

before termlnat_ng the test to ensure thal comb_stor perfocmance had not

changed. Testing was conducted In this manner wlth the four test fuels at

the high pressure condition for each burner length to establlsh the effect

of fuel chemical properties on soot loading. Upon completion of

fuel-effects testing wlth a given burner configuration, either similar

tests were conducted at reduced pressure, or the burner was shortened and

similar tests performed wlth the shortened burner. For the

reduced-pressure tests, the fuel nozzle was replaceC wlth the appropriate

nozzle defined for the 0.8 MPa pressure condition Ourlng spray evaluation

tests. Each of the reduced-pressure tests was again Initiated wlth Jet A-U

to ensure consistent burner performance before gathering data wlth Jet A

and ERaS test fuels.

Data were not gathered at the 0.3 MPa pressure. Durl,-g lasts at 0.8

MPa, the soot loading was quite low at certaln condltlons so that

determlnatlon of fuel effects was difficult. Since soot concentratlon el a

lower combustor pressure would have been further reduced, the beneflts of

testin_ at C.8 MPa were mlnlmal.

22
For a given fuel, fuel-air ratio, and combustor pressure, data were

acquired In the following manner. With airflow and fuelflo_ par_.eters

properly set, the probe flow was del _.Jered • through the soot sampl Ing

system (but bypassing the filter) at e rate equivalent to the sampl Ing

rate. The coolant flow through the heat exchanger was also adjusted es

necessary to maintain sample flow temperature below 400K at the transfer

line entrance. The sample temperature at the probe exlt was observed, and

quench flow added wlth the shorter burners If this temperature was

slgnlflcantly higher than that measured wlth the full-length burner. With

the sample flow properly conditioned, a mlnlmum of three mass samples were

acquired on prewe!ghe¢ teflon fllters. Since the sampl Ing times to acquire

the mass loedlng were were relatively long, three smoke samples and three

data scans were normally acquired durlng each of the mass sampl Ing periods.

M_ss samples were weighed and smoke numbers were calculated fro_ the smoke

samples immediately after acqulsitlon. These data were checked for

co_.slstency, with m_-e samples gathered If any sample weights differed more

than approximately 20 percent of the mean. For test condltions where

optlcel data were acquired, the laser beam was passed through the combustor

exhaust te permlt scattering and transmlsslvlty data to De acqulred wlth

the data system for most of the date scans. Several data scans, however,

were acquired with the laser beam blocked In order to acquire radiation

date.

After completion of ates, sequence, the burner was shut down In the

fol lo_ing manner. Purge gas was reestabl Ished through the sempl Ing probes

to avo!C Ingestion of unburned fuel. Fuel flow was terminated and the fuel

lines Immediately purged. All systems were secured If tests planned for

the day were completed. Otherwise, the test fuel was changed and the Jet

A-U/ test fuel sequence described above was executed again.

Data Acqu_sltlon and Reduction

The complete set of test data was recorded by means of an automatlc

data acqulsltlon system which stated the lnfocmatlon on magnetic tape for

subsequent computer pro_esslng. The date _yst_ accepted data on up to

Z3
25 channels, 10 provided wlth signal conditioners, and the remainder

compatible wlth preconditioned Input signals. The system was capable of

controlling and accepting data from submultlplexers such as pressure and

thermocouple scanning switches. The data channels were scanned

sequentially at • rate of 12 channels per second and whenever a

submultlplexer was connected to e channel, all ports were sampled before

preceedlng to the next channel. An analog-to-dlgltal converter dlgltlzed

the data and an lncrer,ental magnetic tape recorder storecl It for subsequent

computer processing. The format of the tape was structured for

compet]bllli_/ wlth the UTRC UNIVAC 1110 dlgltal computer.

The date system _agnetlc tape was reduced by use of an existing

computer program. Th,s code applies the appropriate calibration factors to

each signal to provide engineering units for pressures and temperatures for

calculation of parem,eters of Interest. Among those se;ected for this

program were: airflow rate, fuel massflow rate, combustc_ reference

velocity, fuel-elr ratio from metered flows, particulate slze and number

density (using Iook-up tables generated by a code for Mie-scattered light),

and ideal ccxnbustion temperatures for the overall combustor. Averages of

pressures and temperatures which ch_racterized the Inlet airflow or

combustor exhaust were also calculated. The output from thls data

reduction code was a Summary Table which displayed all measured and

calculated parameters for every data point. This Table was reviewed for

spurious measurements (e.g.p open thermocouples) wlth hand-recorded data

Input If available. Also, Items not acquired by the data system (e.g., SAE

smoke number) were entered Into the Summary Table.

24
SECTION V - RESULTS

Particulate Concentration and Smoke Number

Metered samp'es from a probe positioned 7 cm downstream of the

co_bustor exlt cenferllne were filtered to determine soot mass loadlngs.

The data are presented as particle concentrations (PC) at standard

conditions, mg of soot per standard cubic meter of samp!e. Figures 18-21

show the concentrations as a function of normailzed combustor length for

the four fuels that were burned. Each data point represents an average of

3 to 5 samples. Data are shown for the full-length combustor (I/L = 1.0)

and flve length reductions corresponding to the sequentla! removal of flve

louvers.

The scot loading generally Increased wlth the roT, oval of each of the

first three louvers. ConcentraTions measured wlth three louvers removed

(I/L = 0.554) are an order of magnitude larger than those gatherej with the

full-length combustor. This trend Indicates that significant soot

oxldatI_n occurred In the secondary zone. Soot masses gathered wlth the

flve-lcuver c_bustor operating at the hlgh fuel/air ratio with all four

fuels {and at all three fuel/alr ratlos wlth Jet A) are not appreclably

different fro_ the full-lengt_ resultsu Evidently little soot oxidation

occurred ',ear the cOmbustor exlf for these conclItions.

C°ncentra+ions measured wlth the two shortest burners do not fo#lo_

the tren_ of Increasing soot ioadlng Inside the combustor. With the

exception aT date gathered wlth the one-louver combustor (I/L =0.27) at the

highest fuel-air ratio, concentrations are comparable wlth levels measured

wlth three louvers on the burner. However, these levels are no + considered

to be representative of the overall soot concentration in the combustor

front end. This co_buslor utilizes a diffusion fia_e In the primary zone

located upstream of air jets admitted In the first louver. Soot production

In such a diffusion flame apparently Involves fuel pyrolysis foll owea very

quickly by nucleation and growth near the flame front (Ref. g). Soot

levels should peak jr, the vlclnlty of the production sites In the primary

zone and then decrease due to oxidation in the co_bustc_ secondary zone.

This trend was Indlca?ed by case-mounted radiometer measurements in the

25
previous program (Ref. I). Since all measuremenes In this experlment were

obtained downstream of the primary zone, soot concentratlons were expected

to _r.crease as the combustor was shortened for all conflgurations tested.

The low concentrat!ons measured wlth short burners can be explained by

recognizing that the flow fle!d in the front end of a practical combustor

tend: to be nonuniform. Calculations using the nom.lnal llner pressure drop

of 17 KPa indicate that the combustion alr Jets penetratlng through the

louvers will reach the combustor centerllne. The centerline region would

be dlluted by the jets and exhibit lower soot concentrations. In addltion,

the dlffus!on flame, which follows the fuel spray, tends to be spacYally

nonuniform wlti_in a transverse plane and could reinforce the

nonunlformltles created by the dilution jets near the combustor centerllne.

The sampllng probe was located near the burner exit plane on the centerllne

and !t appears that the flow field was not fully mixed at this point.

One-polnt measurements at the centerllne, then, probably were not

representative of the average flow condltio_ In the combustor front end.

In order tc galn more Insight concernlng the flow fleld In the

combustor front end, gas samples were obtained In conjunction with soot

samples for the two short burners. With the combustor burning Jet A fuel,

a pcr*ion of the sample fro_ the the probe was removed upstream of the soot

filter location and analyzed to determine carbon monoxide, carbon dioxide,

oxygen, and total nitric oxide concentratlons. The carbon dloxlae and

oxygen data were used to separately calculate the local centerl!ne fuel-air

ratio (f/a). As shc_n In Fig. 22, the two emlssion measurements Indlcate

nearly the same f/a. These fuel-air ra+los, however, are considerably

lower than the flagged symbols, which represent the expected average f/a at

those axlal posltlons based on the flow spllts Identified In combustor

alrfl_ cellbratlons (Ref. I). This t/a comparison Indlcates that the

centerllne raglan was diluted and contained below-overage partlcle

concentrations. Centerllne soot measurements wlth the two shortest burner

lengths, then, cannot be vle_ed as belng representatlve of soot levels In

those measurement planes.

Optical diagnostics also indlcate that soot mass ioadlngs were hlghest

in the combustor prlmary-zone raglan. Transmlsslon measurements of Ir_e

26
laser source l!ght both wlth and without combustionwere used to determlne

the combustinostream spectral emlsslvl.+Y (E) at the light source

wavelength (T) according +o:

514

RT, W/O comb- I_T, W comb

RT, W/O co(r_b

where RT = measured radiance either w!thout (w/o) or with (w) combustor

operation. The emissivities for Jet A and )CFB fuels, d!splayed In Fig. 23,

increase wlth decreasing combustor length. This path-length measurement,

then, Indicates that soot loadTng was highest in the burner primary zone

(I/L < 0.3) and then decreased vie oxidation through the remaining burner

length.

Radiation measurements were also made wlth a narrow-angle detector

sensltlve only to vlsible and near IR radlatlon. The detector, then,

sensed only radiation generated along a combustor dlameter by luminous soot

particles. The measured detector output Is shown In Fig. 24 for operation

with Jet A and _ fuels. Radlatlon levels, though quite low with the

longer combustor lengths, Increase slightly with the two-louver

configuration and Increase slgn!ficantly wlth one louver on the burner.

Though higher temperatures at the one-louver combustor exit contrlbuted to

the Increased radiation, temperature effects cannot account for all of the

Increase. For example, the average exit temperature for the one-iduver

configuration would have to be 2,8 times that of the two-louver burner to

account for the Increased detector output at the Iciest f/a. Uslng the

callbrated air splits, the calculated average temperature Increase Is only

a factor of 1.25. The radlatlon measurements, then, also Indlcate higher

soot Ioadlng Ip the vlcln!ty of the primary zone.

The optical diagnostics also show that soot production increased with

Increaslng f/a. For example, the radiation I_vels (Fig. 24) Increa_ with

higher f/a ratios for the one-louver combustor. Since the primary-zone

equivalence ratios are greater than unity for all three f/a ratios, the
temperatures In the dlffuslon flame structure are nearly the same for the

three cases. Soot located near the prlmary zone radlates at nearly the

same temperature and, there_ore_ the increased radiation can be attributed

to higher soot production. Radiation detected by radiometers mounted in

the combustor dome during the previous program (Ref. I) also increased wlth

increasing f/a, Indlcatlve of higher soot loading at higher f/a. This

trend Is expected because higher f/a was achieved by Increasing fuel flow

while maintaining constant alr_Iow. Higher fuel concentration in the

primary zone led to Increased soot production.

The effect of temperature on soot oxidation can be seen in Figs.

18-21. Particulate concentrations for the three-louver burner are

comparable for the three f/a rat!as. With the longer burners, however, the

concentrafions decrease with increasing f/a. This trend Is directly

attributable to higher combustor exit temperati_res, associated wlth higher

f/a, promoting soot oxidation. Thus, even though more soot was produced in

the primary zone at the higher f/a ratios, higher temperatures in the

secondary zone enhanced particle burnout to overcome the increased

production.

Particulate concentralion dlstributlons obtained wlth the four test

fuels burned at f/a = 0.018, shown in Fig. 25, Indicate the effect of fuel

chemical properties on soot formatlon and oxidation. Since soot

measurements with the one-louver combustor are not belleved to be

representative of the loading In the dome reglon, soot production rates for

the four fuels cannot be deduced from those data. Although soot oxidation

occurred upstream of The three-louver burner measurement location, data

fro_ the longer burners Indicate that oxidation rates for the four fuels

are slmllar. A ranklng of the fuels relative to soot production can be

made, then, using the data gathered wlth the three-louver combustor. A

general ranking in increasing order of soot productlon is Jet A, ERBS,

ERBLS-2, end )CFB. Thls ranking Is consistent wlth the correlation developed

In the previous program (Ref. I) where radlatlon levels In the dome region

were found to be Inversely proportlonal w lth fuel smoke polnt.

Par?iculate concentrations assoclatea w!th burning Jet A and ERBLS-2

at a reduced combustor pressure of 0.8 MPa (Flgures 18 and 20) are

28
generally lower. The changein particulate concentratlon due to the

pressure reduction is shownIn Fig. 26. The data are expressed In terms of

the changeIn concentrailon normalized by the concentration measuredat the

higher pressure. Date for the three-louver combustor(I/L = 0.554) show

lower soot loadlngs at lower pressure for all three fuel-alr ratios.

Thoughsoot oxl_ation occurred inside this combustor upstreamof the

sampling location, these data Indicate that less soot was producedat the

lower combustorpressure. This trend Is logical slnce the reactants are

less concentrated at the soot production site for lower pressure. With

longer burners, the effect of lower pressure is not as strong.

Concentrations measuredat the two lower fuel-alr ratios are reducedat

lower pressure, with the moresignificant reduction at the lowest f/a. At

the highest f/a, however, either the reduction of soot wlth lower pressure

is small or an Imcreasedconcentratlon wasmeasuredat lower pressure. The

impllcation of these date is that although less soot wasproducedat lower

pressure, as Imdlcated by the data at I/L = 0.554, the oxidation rates at

the higher fuel-alr ratios were also appreciably reducedresulting In

similar concentraTlons at the full-length comhustorexit for the two

pressure conditions. The scatter in the high-f/a data for the longer

burners Is associated wlth attempting to ascertain a pressure effect at

rather low soot loading conditions. The uncertainty In the concentration

measurementsat these low soot loadlngs Is equivalent to a slgnlflcant

portion of the sample. For example, PCfor Jet A at f/a = 0.022, I/L

:0.834, andP3 = 1.3 MPaIs 0.49 mg/sm3 whereasat P3 : 0.8 MPaPC Is

0.73 mg/sm3 Themeasurementuncertainty at these loadTngs Is

approximately ± 0.15 mg/sm3. Most of the difference In loading, then,

could be due to measurementuncertelnty.

In conjunction wlth gathering particulate concentration data, SAE

smokenumberdata were acquired as prescribed by SAEARP_179. Data are

shownfor the four test fuels In Figures. 27 - 30. Valld smokesamples

were not acquired with the full-length burner becauseof leaks In the

sampling system for those t_sts. Data from the previous program(Ref. |)

are shownfor that conflguratlon. Somesmokesampleswere gathered while

burning Jet A fuel with the one-louver co_bustor. Thesesamplesyielded

smokenumbersclose to 100. S;nce this technlque has low resolution et

hlgh smokenumber(SN) and the other more sooting fueis would have provided

29
even darker deposits on the filter, detailed smoke samples were no,_

acquired with the one-louver combustor.

The SN data follow trends similar to those noted with the PC data. SN

increased as the combustor was shortened except when the flrst louver was

removed. SN's for the five and six-louver burners are nearly the same.

SN's gathered w lth the two-louver combustor agaTn are not representative

due to dilution of the combustion products near the centerllne by the

dilution jets and nonunlformitles In the flame pattern. SN varies

inversely with f/a for the longer burners but Is nearly constant for the

three fuel-alr ratios with the three-louver burner. The effect of fuel

chemlcal properties and the effect of reduced pressure, as sho_n in Figs. 31

and 32, respectively, are also similar to the observations developed

concerning the PC data.

Smoke number Is a common and a relatively easily acquired measurement

to document turbine eng!ne exhaust smoke. A smoke number, however, does

not reflect any of the physical properties of soot. A correlation between

PC and SN would allc determlnatlon of soot mass loading fro_. SN data. For

this reason, the correlation of PC and SN data from this experiment was

quantifle¢ via a regression analysls. Fig. 33 depicts the varlatlon of

particulate concentratlon with smoke number. The dala polnls represent all

test con_llions: four fuels, three fuel-air ratios, and two combustor

pressures. The relatlonship determlned from the regression analysis, shown

In Fig. 33, Is:

PC = 0.177 SN 1"234

(100 - SN) 0"360

_, R2 = 0.91

where R Is the correlation coefflclent. Thls formul_tlon correctly

models the asymptotes of the PC/SN relatlonshTp. As SN decreases to zero,

PC must also approach zero. Slmllarly, at high soot loadlngs, PC must

approach Infinity as SN approaches I00. Thus, the function has an "S"

shape In Fig. 33. The high value of the square of the correlation

coefflclent indlcates thai th_s expression is an excellent flt to the data.
Champagne (Ref. 10) has also looked at the relationship between soot

loading and smoke number using data gathered by C. Stamforth from the

exhaust of a J79 turbojet engine. A correlation of Stamforthfs Initial

data was very poor. Assuming that variations In carbon partl=ulate size

caused the poor correlation, data were gathered using a two-staged p_rtlcle

separator. The dlvlslon of particle diameter was estimated at one micron.

A good correlation wlth smoke number was obtained using only the small

parlIcle weights. This correlation Is shown as the middle curve In Fig.

33. Stamforth concluded that the large particles, which accounted for zero

to 50 percent of the total carbon weight, added little to the smoke number

values. The actual particle concentrations for a given smoke number, then,

were assumed to be anywhere from zero to 100 percent greater than the small

particle concentrat!ons. This upper limit Is Indicated by the upper curve

In FI_. 33.

A maln conclusion from Champagne,s work is that the correlation

between SN and PC will depend on particle slze. Mie scattering data, which

wlll be shown below, Indicate that the particle diameter In thls experiment

only varied from 0.2 tc 0.25 micron for all test conditions. Thls

relatively uniform particle slze strongly contributed to the good

correlation of the dtta from this experiment. The dlfferenc_ between

Stamforth,s correlation and that from this work can probably be attributed

to the presence of smaller particles In this experiment.

Particulate Size and Number Density

A ch_racteristlc slze and number densll 3, of the soot exiting the

burner on Its centerl Ine were de termlned from light scatterinq

measurements. Number density data gathered for the test fuels Is shown In

Fig. 34 - 37. Data obtained during the previous program are also shown

and agree reasonably well with results from this test. Differences are

Incllcatlve of the uncertainty associated with thls measurement.
Trends described prevlcusly concernlng the soot loading and smoke

number data are evident. The lowest number density at the exit of the full

combustor was measured at the highest f/a. This agaYn points out the

vlgoreus oxldat_on mechanism in the burner secondary zone. Number

densities assocleted wlth the three-louver combustor are less affected by

f/a and are higher than those measured wlth the full-Xength combustor.

Number densltles calculated for the 1_o-louver co_bustor are lower than

those obtained with the three-louver burner due to the nonunlformltles

described previously. Limlted data taken wlth the one-louver combustor

operating with Jet A fuel a_ f/a = 0.018 shc_ a drastically reduced number

density. Evidently the high partlcle concentra_lons in this reglon,

Ind!cated by the emlsslvity and radlatlon data (Figures 23 and 24),

scattered the laser beam resulting in significantly reduced po_er at the

probe volume. The scattered slgnai frc_, the probe volume, then, was also

reduced Yielding abnormally tow number density. Number denslty as a

function of fuel type ;s displayed In Fig. 38 for f/a = 0.018. As

InQlcated by the soot and smoke measur_._enes, number density responded to

fuel chemical properltes, Increaslng for fuels with decreased smoke point.

Limited number density data were acquired with Jet A and ERBLS-2 fuels

nt reduced combus_or pressure (Figures 34 and 36). As expected, number

density Is !ower _t reduced pressure. Reductions wltt Jet A, however, are

_Isproportienately larger than reductions observed with sc_t loadlng and

smoke n_mber at th!s pressure condition. An explanation for these ;ow

number densities has not been established.

Particle slze, as determlned from scatterlng _easur_ents, Is sho_n In

Fig. 39. Based on Ref. 11, com bustor soot partlcles are mature

agglomerates of large numbers of prlmary soot spheroids. These dlemeters

are assumed _o be representetlve of the slze dlstrlbu+ion of the

agglomerates. It must be recognlzAd, _owever, that slnc? light scatterlng

slgnals are greatest for large particles, these dlemeters are b_ased _oward

t_e larger particles ef the dlstrlbut;on. These data show thal partlcle

s_ze is Invarlant wilh respect to fuel chemical properties and c_bustor

pressure. Using Jet A data as the reference, partlcle dlemefer Is

approximately 0.25 l_m for the three shorter buri_ers. The relative
_'.nstancy In pertlcle slze Immediately downstream of the prlmary zone

Indlcetes that the spherolds agglomerated qulckly. The average partlcle

dl_eter ev!Oently decreased between the third end fourth louvers and then

remained constant, Particle dlameter for the full-length burner is

approximately 0.21 /_m. Thls slze, which Is nearly Identlcal wlth the

particle slze determlned In the prevlous program, is apparently much

smaller than that measured by Stamforth, where e slgnlflcant portlon of the

sample consisted of partlculates larger than one mlcron. The correlation

between soot loading and smoke number In thls experlment (Flg. 33), then,

should and does fall below Stemfeeth's correlation.

Number density and particle slze can be used to calculate the volume

fract:on occupied by the soot partlcles. In order to correlate thls volume

;raction w lth the particulate mass concentrations previously presented,

however, the volume fraction must be calculated for standard condltlons.

Tempera.*ure at the probe volume Is requlree to perform thls calcuiatlon.

This temperature was not measured durlng the test progra,r, because of the

high exlt temperatures that were produced as the combusto_ was reduced In

length. The emission date gathered with the two-louver combustoc (I/L =

0.413 In Fig. 22) was used to celcuiet,_, temperatures for that

¢onflguration. Temperatures at the exlt of the full-length burner were

celcu!ated based on the measured overall fuel end 81r flows. Temperature

was assumed to decrease llnearly between these t_o points. The resultant

correlation obtained wl_h this temperature dlstrlbutlon Is shown In Fig.

40. W!th the exceptlon of the low-pressure data gathered wlth Jet A fuel,

concentratlon and volume fraction correlate well. A reasonably good

representation of the date (not Including the low-pressure Jet A data) was

generatecl vla a regresslcn analysis.

The ratio of particulate concentration to particulate volume frectlon

is particle density. The denslty dlstrlbutlon obtained from fhe data shown

In Fig. 40 Is contained In Flg. 41, The data Indlcate that the average

partlcle density only decreased slightly as the parflcles moved through the

combustor. That the partlcle denslty tended not to change can also be

deduceo from the expresslon developed In the regresslon analysls tFlg. 40)

of data from all combuslor lengths. The exponent In that expresslon Is

close to unlty Indlcatlng that concentretlon Is nearly proportional to
volume fraction end, hence, that density does not change slgqlflcantly over

the range of test conditions. The value of the partlcle density Is lower

than that for sol Id carbon, which Is approxlmately 2 g/cm 3. The lower

particle denslt_/ Is conslstant wlth the concept that the particles are

agglomerates of smaller sol Id spheroids. The particle density will always

be less than 2 g/cm 3 because of the space between spherlods and will be a

function of the type of chain-like structure created during the

agglomeration process. Samples collected by Wyatt et. al. (Ref. 12)

downstream of 8 disk-stabilized flame also contained particulates with

densltles lower than that of carbon by a factor of 3 to 5. Note that the

Ioi-pressure Jet A results yield partlcle densltles 5 to 7 tlmes that

calculated for the high-pressure tests. Slnce the particle dl_eter for

the two pressure condltlons ls nearly the same, these data Imply that these

agglomerates were more tlghtly packed at low pressure. There are

apparently no physical arguments that can be used to explain this tendency.

The number of small spheroids In the agglo_erafes of this exper!ment

can be estimated. Bonczyk and Sanglovennl (Ref. 11) determined from

photomicrographs of typical soot samples that the average spheroid dl_meter

is approximately 209 A. These small particles can be assumed to be sol_d

carbon wlth a denslty of 2 g/cm 3. For an average agglomerate denslty of

0.4 g/cm 3 and dlameter of 0.2 #m, the average number of spheroids per

agglomerate Is 200.

34
IlL

IP

SECTION V I - CONCLUSIONS AND REOOMMENDATIONS

Based upon data acquired In the combustion test program, the following

concluslons have been made:

I. The soot oxidation mechanism In a gas turbine combustor

secondary zone Is very vigorous and strongly depenOent on the combustion

product temperature. Oxidation rates do not depend strongly on fuel type.

2. Soot particulate slze distribution decreases fran a

characteristic diameter of 0.25 m to 0.20 m as the soot particulates

oxidlze.

3. Soot mass loading and SAE smoke number correlate well for gas

turbine combustors that produce small particulates.

4. Soot particulate denslty Is approxlmately 20 percent that of pure

carbon. This lower density is consistent with the concept thai the

particulates are chaln-llke structures composed of small particles of pure

carbon.

5. Combustor pressure affects soot production, wlth more soot

produced at higher pressure. Combustor pressure may also affect soot

oxldatlon rates.

6. Fuels with a hlgner smoke point produce ,ass soot in a gas

turbine combusto, .

7. Soot loading near the primary zor_ of a gas turbine combustor Is

three-dimensional due to the combustion Jets passing through the louvers,

It Is recommendeO that the fol lowing Investlgatlons be conducted to

addres_ the following technology needs as Indlcated In this program:

35
I. A phenomenologlcalmodel of soot production and consumption In a

gas turbine combustor needs be developed and evaluated. As chemical and

fluid mechanical processes together control soot production, both

Influences must be Included. Data are required to evaluate the model.

2. Development of fundamental mechani_s and models of soot

pro(luction from aviation type fuels.

3. Quantitative evaluation of pressure Influence on soot

procluct Ion.

4. Data to identify fuel chemlcal property Influences associated

wlth the use of air-blast fuel injectors In gas turbine combustors.

36
REFERENCZS

I. Rosfjord, T. J.: Avlatlor - Fuel Property E.fects on Combustion.

NASA CR 168334, February, 1984.

2. Clark, J. A.: Fuel Property Effects on Radiation Intensltles In a Gas

Turbine Combustor. AIAA Journal, Vol. 20, No. 2, pp. 274-281. February,

1982.

3. Belial, D. R. and A. H. Lefebvre: Combustion Performance of Gas

Turbine Combustors Burning Alternative Fuels. AIAA Journal of Energy, Vol.

3, No. I, pp. 50-54. January, 1979.

4. Van de Hulst, H. C.: Light Scattering by Small F:Jrticles. Wiley, New

York, NY 1957.

5. Kerker, M.: The Scattering of Light and Other Electromagnetic

Radlaslons. Elsevier, New Yerk, NY, 1969.

6. Dier_endJlan, D.: Electromegentlc Scattering of Sperlcal

PO:ydlsperslons. Elsevier, Ne_ York, NY 1969.

7. Bonczyk, P. A.: Measurement of Particulate Slze by In Sltu Laser

Optical _thods: A Crlfica! Evaluation Applied to Fuel Pyrolyzea Carbon.

Combustion and Flame, Vo!. 35, pp. 191-206. 1979.

8. Lln, B. Y. H, and K. W. Lee: Efficiency of Membrane and Nuclepore

Filters for Submlcrometer Aerosols. Envlornmental Sciences and Technology_

Vol. 10, No. 4, April, 1976.

9. Glassman, I.: Phenomenol oglcel Models of Soot Processes In Combustion

Systems. AFOSR TR 79-1147, 1979.

37
10. Champagne,D. L.: Standard Measurementof Alrcraft GasTurbine Engine

Exhaust Smoke. Presented at the ASMEGasTurbine andProducts Show,

Houston, Texas, Mar. 28 - April I, 1971.

II. Bonczyk, p. A. end J. j. Sanglovanl:

of Soot In a Burning Fuel Droplet Stream.

1983.

Optlcar and Probe Measurements

UTRC Rep. UTRC 83-25, June,

12. Wyatt, W. R._ J. A. Clark, J. E. Peters, and A. M. Mallor: Size

Distribution and urface Area Measurements of Gas Turbine Cx_nbustor Smoke.

Journal of Energy, Vol. 3, No. 6, pp. 285-290. September - October, 1979.

38
TABLE I - FUEL ANALYSIS METHODS

Hydrogen (wt pct)

Flash point, tag closed [K)

Dlstlllatlon (vol pct at T [K]]

Freeze point (K)

Smoke polnt (ram)

Speclflc gravity Cat 289K)

Vlscoslty at 293 (cst)

Vlscoslty at 253K (cst)

Net heat of combustion _'MJ/kg)

Mercaptan sulfJ_r (wt pct)

Total sulfur (wt pct)

Nitrogen (wt pct]

Saturates _vol pct)

Oleflns Cvol pct)

Aro_,atic (vol pct)

Naphthalenes (vol pct)

Mass spectrometry for hydrocarbon types (wt pct)

Surface tension (dyne/cm)

ASTM D 3178

D 56

D 86

D 2386

D 1322

D 1298

D 445

D 445

D 240

D 3227

D 2622

Antek Chem I Ium I nescence

D 1319

D 1319

D 1319

D 1840

D 2425

Tens !ometer

39
TABLE 2 - Fuel Analyses

_ _ XTB

Speclflc Gravity at 289K 0.8165 0.8388 0.8612 0.8751

Flash Poln_ (K) 319 326 3!6 315

Freeze Polnt (K) 226.5 243 247 <206

Smoke Point (mm) 20.3 12.7 10.3 7.4

Net Ht of Combustion (MJ/kg) 42.88 42.48 41.86 40.78

Viscosity at 253K (cst) 5.39 5.69 5.00 1.85

Vlscosil 7 at 293K (cst) 2.02 2.07 1.89 0.95

Surface Tension (dynes/cm) 26.3 27,1 27.6 28.50

C (wt pc¢) 86.04 87,02 87.85 90.30

H (wt pc_) 13.70 12.84 11.76 10.24

Mercaptan Sulfur (10 -4 wt pc_) <5 <5 <5 <5

Total Sulfur (wt pct) 0.06 0.12 0.11 <0.01

Nitrogen (_/mL) 7 81 75 <5

Saturates ( ol pct) 78.1 67.2 47.7 0

Oleflns (vol pc_) HC-FIA 1.7 1.4 1.3 0

Aromatics (vol pct) 20.2 31.4 51.0 100

Naphthalenes (wt pcT)- UV 2.44 16.34 17.41 0,43

Aromatics (vol pcff) HC-Mass 5pec 22.0 29.9 47.5 100

Naphthalenes (wt pet) 1.68 11.71 22.97 0.01

Hydrocarbon Type by Mass Spectrometry (wt pct)

Total Saturates

Paraffins

Moncyclo Paraffins

Dlcyclo Paraffins

Tricyclo Farafflns

Tota! Aromatics

Akyl Benzene

Indanes

Indenes

CI0 Napfhalene

C11* Napthalenes

Acenanapthenes

Acenanap_halenes

TrlcyIIc Aromatic

73.4 65.8 47.3 0.0

34.9 42.6 31 .I 0.0

33.7 15.3 10.5 0.0

6.2 7.1 5.3 0.0

0.6 0.8 0.3 0.0

24.6 34.2 52.7 100.0

18.0 16.9 20.1 100.0

4.9 4.7 7.5 0.0

0.0 0.2 0.9 0.0

1.7 0.4 0.5 0.0

0.0 9.2 17.j 0.0

0.0 13 3.2 0.0

0.0 0.8 1.8 0.0

0.0 0.6 I.3 0.0

4O
TABLE 2 - Fuel Analyses

(continued)

Dlstiilatlon (K)

Vol

Off XTB

IBF 438 446 424 430

5 452 457 437 432

10 459 462 442 433

15 463 465 448 434

20 466 467 452 434

30 473 473 462 435

40 479 479 47_ 435

50 486 486 486 436

60 492 493 499 437

70 500 502 514 439

80 509 514 530 439

90 52i 537 556 442

95 531 563 580 445

41
T/_I_E 3 - Nozzle Cheracterization

Nozzle

SMD (/Lm)!lncluded Cone Angle (d6ol

Fuel Flowrafe (kglhr)

27 3O 37 73 82 100 118 133 162

8 48/82 40/80 28/77

9 60/80 52/77 35/78

10 66/80 60/78 44/78

18

20

22

42182

53/80

67175

3O/8O

42/80

53/76

6/77

16/79

31/74

32

35

57/81

71/78

42182

56/76

9177

23174

42
TABLE4 - CombustorOpenAree Dlstribution

Dome

Louver I

Louver 2

Louver 3

Louver 4

Louver 5

Louver 6

5_

Area Distribution

Diameter (_

Cooling 60 1.78

(4 rings) 60 1.47

60 1.47

60 1.09 4.09

Cooling 96 1.98 2.96

Combustion 6 12.7 7.13

Cooling 96 1.98 2.96

Combustion 6 12.7 7.13

Cooling 96 1.98 2.96

Combustion 6 12.7 7.13

Cooling 96 1.98 2.96

Cooling 48 1.98 1.48

Combustion 6 12.7 7.13

Cooling 48 1.98 1.48

-j
TABLE 5 - Liner Effective Area Distribution

Section

Sw Irl er

Dome

Louver 1

Louver 2

Cooling

Coollng

Combustion

Cooling

Louver 3 Cooling

Combustion

Louver 4 Cooling

Louver 5 Coollng

Combustion

Louver 6 Cooling

Total Liner wlth Swlrler

Effective _ea (cm 2)

3.0

3.0

2.5

4.6

2.5

4.6

2.4

4.5

2.6

1.2

4,6

1.3

36.8

Percent of Total

_jm!_h Swlrler)

8.2

16.3

23. I

35.6

42.4

54.9

6! .4

73.7

80.7

84.0

96.5

I00.0

100.0
TABLE 6

AirFlow and FuelFIow Conditions

Alrfiow Conditions

Condltlorl

Mass FI_ Approach Pressure

(__

Approach Temp.

(K)

1. High Power 1.82 1.3 700

2. Reduced Pressure 1.45 0.8 700

Fuel-Air Ratios

Exlt

T_perature

1240

1340

1470

0.0150

0.0180

0.r220

Fuel

.0153

.0182

,0223

i_SLS_2

.0153

.0184

.0224

XTB

.0156

.0188

.0230

I

45
R85-956760-2_

t_

__J

©

p.-

(.0

iJ.

©

t_

C

©

Fig. 1

/

/

40--

20 -

C

/

/

Y

,/

o/

/

0

/

,

/

//

2O ,I0 60 8O

TOTAL AROMATICS BY FlA, ASTM 1319 fVOL Pcl}

loo

Comparison of Total Aromatic Content for Two Analysis Techniques
24

(D

G_

20

_O

I-.-

C,

Ck

C3

O)

z

__J

2

T

Z

16 --

_

4 _

/

/o

0

/

0

/

/

IDEA,. C. _, ;.'T;

/

/

/

/

O

/

/

I 1 I !. f

4 8 12 16 20 24

NAPHALENE BY UV SPECTROPHOTOMETRY

ASTM 1840 (wt PCll

Fig. 2 Comparison ot Naphthalene Content for Two Analysis Techniques

115-g-67-2
R85-956760-21

jE T

_UNDE_G4qOuNC

STOq,t, GE,

TL_RBINE

METEP_

r','_ZZ_E j_t

I _

%

..... t ...... \

S '--'Ez_',z,_',ZE=

SC c_dBBE '_

Fig. 3 Fuel Spray Characterization Facility

IS-.g_|.,.. 3
R85-956760-21

¢-,

09

>..

<_

80

6O 9

8

JET A FUEL

80 (:leg HOLLOW CONE SIMPLE×

INJECTORS WiTH ,NDiCATED

NOZZLE NUMBER

22

2C

o I 1 I I I

0 20 40 60 80 100 180

\

1 1 1

120 140 160

FUEL FLOW (Kg/h)

Fig. 4 Influence of Fuel Flow on Jet A Spray SMD for Several Nozzle Sizes

14 5 49 - I
R85-956760-21

z""

_J

I-.-

<

cr

©

._J

!.,L..

._J

180

160 --

140 --

120 -

_00 --

80 -

6C --

40 -

20--

0

0

1 _1

5 10

JET A FUEL

80deg HOLLOW CONE

SIMPLEX iNJECTORS

NOZZLE NUMBER

SMD = 20pro q

j

35 40

Fig. 5 Injector Size Required Io Achieve Atomlzatlon Level
R_5-95t_76@-2]

ORIGINAL PAGE IS

8E,--9-_ 7 4
R85-956760-21

ORIGINAL PAGE IS

oF eooe O_JAU'/y

a) SIMPLEX PRESSURE ATOMIZING INJECTOR

D) AIRFLOW SW![qLER

t32 199 R

Fig. ? Fuel Nozzle and Air Swirler

83 7- 29-4
°:

R85-956760-21

COMBcfSTION

DOME _ --

5O

4O

"5

"6

c 30-

(D

20-

O

fie

10

0

0

L_qqv,,., J P_q©BE SET

'° l

D l ¢ :_-

D_NC'ES .JM _ j-.,T _,. :

BJnNE '-" C-.,." l::).:t

_kZlM_jx_

£", _"OLE S

ON _OL.ES

BETWEEN HOLES

BETWEEN HOLES i

,D 8D

1:3

tb

D

O 13

C13

>e--...X

1 I I 1 I I ,

2 4 6 8 10 12 14

POSITION ALONG CAN crn

Fig. 8 Primary Airflow Split in Goneric Combusfor

62-8-110-1
R85-956760-21

DiSC AL,

-- _ AS,Z,E S_ SPOOLS

APTER

_ <HA 'S,

BAC_

PRESSuIqE

VALVE

AIR PREPARATION

SECTION

I I

I TEST AND I

I

INSTRUMENTATION I EXHAUST

I SECTIONS I SECTIONS

I

I I

I

Fig. 9 Aviation-Fuel Properly Effects Test Facility
_" R85-956760-21

Z ,,_

y,r _

_r

[D"

r--_

I

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C

;,4

()-

o

0

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R85-956760-21

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R85-956760-21

I145)

!0

1(1351

100 -

r='_ 94-066

/

1 I I I

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PARTICLE DIAMETER _.m)

Fig. 13 Scattered.Light Ratio Dependem(..J o,, Particle Diameter
R85-956760-21

\ p

0

0

PMT

w

1

Fig. 14 Layout of Particle Sizing Apparatus

|S--g-ST-6
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J I

ORIGINAl P_GF iS

PO0_ QUALRy

• °_ - .

0

era

c

u

0.

e,,

0

_J

i1

(_5 3 72 15
_" R85-956760-2_

i

_'" ; • t :- :.z] ,z z

\/

Fig. 16 Optical Setup for Visable Transmission/Radiance Measurements

85-3,-72-31
F185-956760-2 !

p

.i

+

._ E

a. E

_._

<,

Z

0

0

Q.

2

a.

a.

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Ig

X

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0

84-4-34-1
R85-956760-21

tO0 0

i

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E 100

z

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z

t..1_1

(D

Z

O

(.D

u_l

l--

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ro

_.- 10--

rr

01

0

1

O2

Fig. 18.

O 00'5 O " -

Q C'0_8 • ::6

A C 022

I I

04 06

COMBUSTOR LENGTH t'/L

1

O8

Sool loading for Jet A fuel

115- 9-29-3

"!
R85-956760-21

1000

P- " " 3 t',,'1_a

o

d

t"1 : --_,

01

0

J

J J 1 I j

02 04 06 08 10

COMBUSTOR LENGTH, I'/L

Fig, 19. Soot loading for ERBS fuel

@@. @-2@-4
1000

! d P3 - MPa

00,L':E 0 _3

D _. 018 • 08

0 1

0

I . I I 1 _m

O2 O4 06 08 10

COMBUSTOR LENGTH _"L

Flg. 20. Soot loading tnr ERBLS-2 tuel

8_-g-2g-5
R85-956760-21

O 00_5

!:::} 00_8

0022

100 0

P_=_ 3MPa

,)

E

E

z

©

I-,.-

rr

Z

(D

Z

O

(..'_

(D

Et'l

100

10

0 1

0

I I

02 04

I

05 08 I0

COMBUSTOR LENGTH. t'/L

Fig. 21. Sool loading for XTB fuel

8@-9-21-@
R85-956769-21

®

O

<L

rr

r"r

.<

,,U

!.L.

D,.,;

z

rr

I11

l,,-,-

z

(._)

.,.a

C.)

O

._1

C O8

faO.EPALL

tl --'_

SPEObESMF _,SU_ED

O zo 2

m,.'ER_,GEt a BASES,

ON COMBuST,Om CA,__BmA'_3",. I_EF 2i

JET A FUEL

0 06

0 04

OO2

d

d

II

lJ

d

d

g

i I I I

0

O 02 04 06 08 1 0

COMBUSTOR LENGfH, I:'IL

Fig. 22. Local centerline fuel.air ratio based on gas emission measurement

"i

85-g-2g-7
R85-956760-21

fa

0 CC_

3 _22

P3 _ MPa

0 _3

• ,:_8

©

I--

_Z

©

z

r1 O0

075

0 59

025 -

O

00_-_

075

0 50 -

0 25

oo- !

O2

XTB

Z_

0

Z_

JE" A

O

0

g

04 06

COMBUSTOR LENGTH, *'/L

_L

O8

Fig. 23 Emissivity at combustor exit
r R8. _956760.21

ir

50--

:>

E

t,-.

G_

I--

©

r'r-,

o

(..D

!.--

.i,.

C_J

25

0 C

I

O2

P_=I ,_MPa .t

O 00!5

O 0078

1% O 022

XTB

13

O

A

.B. Q v

04 06

COMBUSTOR LENGTH. t'/L

i

O8 10

i:

E

I-,.-

Z.)

o

Pr

o

I--

I.U

I.--

LL,

,m

25

0C;

JET _-

&

0

0

O2

Fig. 24

A

COMBOSTOR LENGTH. [_L

Radlalion at combus_or exit

I

O8 _0

85-9-29--8
I-.,-

R,65-95676C.21

E

CT:

E

!

2:

o

l,,-,-

2:

,.,,U

(D

Z

©

(D

,.IJ

t,.--

.<

(2,

I-.-

rT"

"1:

LL

!0-

01 _

@

FLIE_

0 JET _.

rl EqBS

0 E_B_S2

A XT B

o

t a = _",:" 8

Fig. 25

L"--_-----Z--_- I I

02 C'a 06 08

COMBOSTOR LENGI'-H. f'L

Fuel effects on particulate concenlration

lO

85-9- 29-10
10:

' a _JE.

O 0 t':_ O -E" A

A ; (,2_

co

O

o

r_

c_

rt

Z

©

DL

Z

(D

Z

©

O

_J

_J

O

rr

<_

n

Z

_j_

rm

<

-f

O

O--

r_

0 5rj

C D

| 0

0

0

0 •

-10 I I I I

C; 02 04 06 08

COMBUSTOR LENGTH - t'/L

Z_

10

Fig. 26 Effect of combustor pressure on particulate concentration

85--9-29--11
L_- R85-956760-21

dD '_*_ F_OM qEF 2

100

P- _ MPa f_a

0_3 0 CC:_

• ,:8 O 0o,8

0 022

l:3:::

I,A,J

rr_

Z

I,aJ

©

(,,o

iI,

C/3

8O

60

40 -

2O

0 0'

II

_, I L I

02 04 06

COMBUSTOR LENGTH, f'L

08 10

Fig. 2.7 SAE smoke number for Jet A fuel

85-0-29-12
R85-956760-21

l..,u

_z3

z

_d

©

O9

l.,u

<

100 -

8O

60

40

20

O / DATA FROM REF 2

f/a

0 00_5

O 0073

Z_ O02_

P.=I 3MPa

,1

o_

0 02 04

..1

O6

COMBUSTOR LENGTH, I',"L

JI.

O8

Fig. 28 SAE smoke number for EnBS fuel

85-g-29-13
R85-9fi6760-21

100

#- _ Mma fa

_- O £2L

Z

_u

0

CO

l.u

<

CO

6O

40

2O

1 l i

O0 02 04 06 08

COMBUSTOR LENGTH, t','L

Fig. 29 SAE smoke number for ERBLS.2 f,.el

85-9-29-14
A85-956760-21

m

z

_U

©

o3

oo

1O( -

8O

6O

4O

2O

0 ----,-----__Z

0 02

O/ DA'z,, F_OM qEc 2

fa

O-t._

A : o:2

P. =_ 3 M_a

b

4. ± .J J

04 OC 08 1 C,

COMBUSTOR LENGTH I'"L

Fig. 30 SAE smoke number for XTB fuel

06-0-20-16
R85-956760-2_

i00

8S

rT

60

z

L_J

W"

©

,<

co

40-

20-

o I

0 '3 2

FUEL

O JET A

O E_nBS

,_ EPB_S .[

A ×TB

I I I

04 06 08

COMBUSTOR LENGTH, I'lL

10

Fig. 31 Fuel effects on SAE smoke number

85-9-29--18
R85-956760-21

10

't a

O 0075

13 00_ •

0 022

FUEL

0 jET

• ERB.SC

2

z

I

L_J

z 0

0

L_

o0

zI

L_

© -05

z

I

q_

-10

L

• Q

o

O

0

i

,! I I I

02 04 06 08

COMBUSTOR LENGTH. I'I/L

10

Fig. 32 Effect of combustor pressure on SAE smoke number

8_-9-29-17
•, R85-956760-2_

E

E

Z

G

t.--

rr-,

t,---

Z

_.J

o

z

G

o

_J

0

I'-"

IT

13_

100

P::_MP_ FUEL

O L L'f O _ _ O JE- A

C, 022 A EqBLS-2

0 ,_.TB

10

01

,

/ Q

/

O

__ l j I ]

0 20 40 60 8?,

SAE SMOKE NUMBER

¢

100

Fig. 33 Relationship between particulate concentration and SAE smoke number
R85-956760-21

!08

' a P3~M#a O/ RE;

13 00;8 • 08

0 02._

I

b

>;

I--

09

Z

bJ

Q3

Z

107

106

105

0

I

O2

n

&

I i j

04 06

COMBUSTOR LENGTH. t'/L

O8 10

Fig. 34 Number density for Jet A fuel

8F-g -29-18
R85-956760-21

+Lt.

l,'a

O 00_5 O' RE_ 2

n o 0_8

A 0 02Z

108

P-::1 _ MPa

co

I

E

'o

I

>...

t..-

,,,%

z

l.J

tm

I'T

u,,J

r,n

Z

107

106

_e5 I I 1 I •

o 02 04 06 0.8 10

COMBUSTOR LENGTH I'/L

Fig. 35 Number density for ERBS fuel

85--g-, 2g- lg
R85-956760-21

108

d

0:_

f,a CI' _E _- ;

C} 1,'(,_8

072. s

E

I

>-

z

m

:m

z

107.

10 6

105

0 02

!

z i I J

04 0.6 98 1 0

COMBUSTOR LENGTH t'/L

Fig. 36 Number density for ERBLS-2 fuel
9_ R85-956760-2_

i

10 8

CO

E

>-

z

r_

z

107

106

105

0

f ,.-,

D t;'a

P-- =" _ MPa

02

1 1 i

04 06 08

COMBUSTOR LENGTH, I','L

10

Fig. 37' Number density for XTB fuel

85--9--29- 21
R85-956760-21

J

C"

t

>..

i..-

z

t,n

z

108

4,47

106 -

, 5

,0

0

guE_

-- ,-,-.-.--.--..._.._

0 dE7 A

O ERBS

<) ERS:.S.,_

A XT8

fa=CO'S

P3 : " L: MPa

]

J

0_ O4 06

COMBUSTOR LENGTH I'/L

O8 10

Fig. 38 Effect of fuel on number density

85-9-29-_2
R85-956760-21

£.)

l,.--

r

03

0._

0,

O3

03

C?

0 1

03

O2

• L: F" _ t*AF' _

O. "_ 0 _ ,

A . _L

E_RBhS £

I I I I

E_Bb

I I

I I i I

- T A

!

1

1 | I I J

r; ,: (: 4 0 6 0 8 1 0

COMBUSTOR LENGTh,. t'.'L

Fig. 39 A'_erage particle diameter at combustor exit

85-9--29-23
R85-956 _'60-2

10 n

' _, FUEL F • _ tJ;:e

O L'_.:5 0 ,jE[ A 0 " 3

ti) _ :" __ 0 EaBE 0": 8

¢ ×TB

E

E

t

z

f-.

G:.

i,--

z

(.D

z

0

:D

i

ro

t,.

!0

¢' o' o/0, ` 0\\\\

/

o_ I I

10 -4 10-3 10--2

PARTICULATE VOLUt,,1E FRACTION, cmS/sm 3

10-

Fig. 40. Relationship between particulate concentration and particulate volume

_-9-2g-1
R85-956760-21

fa P- _ MPa

o

13 ::'e •_.8

A :. 022

_,2

O"

>

z

I,--

(:1.

ERBLSI2

o

L .L

fiqBS

.1 1

7

20'------------

t I

JE _ A

10 -

0

0

tll

I I !

02 04 06

COMBUSTOR LENGTH, f/L

I

I

O8

8

z_

d

10

Fig. 41 Particle density at combustor exit

I,,._. • -

06-9--20--24
I. Ragor! No.

NASA CR-175030 2. Government_ion No 3, Recil_ent'sCatalogNo,

5. ReportDate

January, 1986

4. Title and Subtitle

"Optical and Probe Determination of Soot Concentrations

in a Model Gas Turbi,:e Combustor"

7. Author(s)

W. A. Eckerle

T. J. Rosfjord

9 Pwfmmeng Orpni_tion Name and Address

United Technologies Research Center

Silver Lane

East Hartford, Connecticut 06108

12, S_n_ring A_y Name and A_r_s

NASA Lewis Research Center

21000 Brookpark Road

Cleveland, OH 44135

5. _p_ernemtarv No_es

6. Perfuming Organization Code

8. Perf_mi_ Orpnizat0on Re_rt No.

UTRC R85-956760-21

10. Work Unit No.

11. Contract or Grant No.

NAS3-24223

13. Type of Report and Period Covered

Contractor Final Report

14. SponlIOri_ Agency Code

Program Manager - J. Biaglow

16 Abstract

An experlmenial program was conducied at UTRC i'o track the variation

In soot loading along the centerl Ine of a generic gas turblne combustor.

The burner was a 12.7-cm die cyllndrlcal device consisting of six

sheet-metal louvers. Determination of soot loading along the burner length

was achieved by acquiring measurements first at the exlt of the ful l-length

combustor and then at upstream stations by sequential removal of liner

louvers to shorten the burner length. Alteration of the flow field

approachlng and within the shortened burners was minimized by bypassing

flow that would have passed through removed louvers In order to maintain a

constan_ liner pressure drop. The burner exhaust flow was sampled at the

burner c=_nterl Ine to determine soot mass concentration and smoke number.

Characteristic particle size and number density, iransmlsslvlty of the

exhaust flow, and local radla+Ion from luminous soot particles In the

exhaus¢ were determined by opl'ical techniques. Four test fuels were burned

at three fuel-alr ratios to determine fuel chemical property and flow

temperature Influences. Data were also acquired at i_wo combustor

pressures. Particulate concentration data Indicated a strong oxidation

mechanism In the combustor secondary zone, though the oxidation was

significantly affected by flow tempeature. Soo? production was directly

related to fuel smoke point. Less soot production and lower secondary-zone

oxidation rates were observed at reduced com,bustor pressure.

17 Key Wor_ (Su_g_"_ted by Author(s))

Gas Turbine Combustors

Soot Concentration

Fuel-Effects

19 ._W:ur_tv _l_,f (ofth_sre_rt)

Unclassified

! 18 Dl$_r_l_ Statement

Unclassified - Unlimited

20 Secur,tv ClaM, f, (of th,s I:_gel 21 No of Plges

Unclassified

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