NASA Contractor Report 168334

Av._aticn,-Fuel Property Effects

on Con,bustion

T.J.Rosfjord

UNITED TECHNOLOGIES RESEARCH CENTER _i*_ :

East Hartford, CT 06108 "_;. ,

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NASA Contractor Report 168334

Aviation-Fuel Property Effects

on Combustion

T.J. Rosfjord

UNITED TECHNOLOGIES RESEARCH CENTER

East Hartford, CT 06108 i

February 1984

N

Nat,onal

/ A

Aeronaut,cs and

Space Adm_nfstratJon

Lewls Resesrch Center

Cleveland,Ohio 44135
ACKNOWLEDGEMENTS

This report covers the investigation performed by United Technologies

Research Center under NASA Contract NAS3-23167. The UTRC Principal

Investigator was Dr. Thomas J. Rosfjord; the NASA Program Managers were

Messrs. Andrew Szaniszlo and James Biaglow. Several individuals at UTRC

and NASA contributed to the success of this program. Mr. Roger Svehla,

NASA, provided valuable imput for the selection of the test fuels. At

UTRC, Mr. Roy Pelmes and Dr. John McVey gave freely of their time in

assisting in the guidance of the effort Messrs. Jan Kennedy and Sid

Russell conducted the fuel spray characterization effort and discerned a

specialized atomization regime. Dr. Paul Bonczyk's guidance in setting up

the light scattering system was essential. Mr. Wayne Eckerle's assistance

in conducting the combustor tests was very beneficial, while Mr. Louis

Chiappe_ta's diligent efforts made the data normalization, precision

analysis and reporting efforts tractable. Ms. Janice Fournier devoted many

appreciated hours to data management and Mr. Ralph Aiello's conscientious

labors were largely responsible for the timely execution of the test

effort.
R84-915908-29

Aviation-Fuel Property Effects on Combustion

TABLE OF CONTENTS

Pa_e

LIST OF FIGURES iv

LIST OF TABLES vi

LIST OF SYMBOLS vii

SUMMARY ix

SECTION I- INTRODUCTION 1

SECTION II - TEST FUELS 3

Fuel Description 3

Fuel Analysis 6

SECTION III- GENERIC GAS TJRBINE COMBUSTOR 8

Combustor Description 8

Combustor Calibration I0

SECTION IV - FUEL SPRAY CHARACTERIZATION AND INJECTOR SELECTION 13

Atomization Goal 13

Fuel Spray Characterization 15

SECTION V - TEST FACILITY AND INSTRUMENTATION 21

Test Facility 21 ',

Instrumentation 22 "

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SECTION VI - COMBUSTOR TEST CONDITIONS, PROCEDURES, DATA i

ACQUISITION AND REDUCTION 28 ;

Test Condition and Procedures 28 i

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Data Acquisition and Reduction 29 j

SECTION VII - COMBUSTOR TEST RESULTS: FUEL-EFFECTS 33 f

General Combustor Operation and Data Quality 33 I

Property Influences 35 !

Chemical

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SECTION VIII - COMBUSTOR TEST RESULTS: CONFIGURATION-EFFECTS 47

General Combustor Operation and Airflow Interaction 47

Configuration Influences in the Primary Zone 48

SECTION IX - CONCLUSIONS AND RECOMMENDATIONS 51

REFERENCES 52

TABLES

FIGURES

APPENDIX - DATA TABLES

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LIST OF FICURE$

]. Comparison of Total Aromatic Content for Two Analysis Techniques

2. Comparison of Naphthalene Content for Two Analysis Techniques

3. Generic Gas Turbine Combustor

4. Fuel Nozzle and Air Swirler

5. Test Setup for Effective Area Determination

6. Primary Airflow Sampling Probe

7. Calculated Combustor Airflow Split

8. Predicted Droplet Lifetime in Primary Zone with 20 Pot Turbulence

9. Fuel Spray Facility

I0. Fuel Spray Mass Distribution for No. 35 Nozzle

ii. Weber Number Regimes

12. Influence of Surface Tension on Measured Atomization

13. Influence of Fuel Viscosity on Measured Atomization

14. Aviation-Fuel Property Effects Test Facility

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15. Air Supply System for Test Rig

16. Test Rig Support Systems and Instrumentation

17. Transpiration Radiometer

18. Operational Characteristics of Transpiration Radiometer

19. Probe Distribution at Combustor Exit

20. Scattered-Light Ratio Dependence on Particle Diameter !

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21. Layout of Particle Sizing Apparatus j

22. Variation of Dome Radiation for Jet A-U Fuel

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23. Axial Distribution of Liner Radiance for ERBS Fuel I

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24. Variation of Liner Radiance for Test Condition I i

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25. Variation of Liner Radiance for Test Condition 3 I

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26. Active Sooting Mechanisms for Aviation Fuels i

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27. Dependence of Dome Radiation on Fuel Hydrogen Content for Condition 2

28. Dependence of Dome Radiation on Fuel Total Aromatic Content for

Condition 2

29. Dependence of Dome Radiation on Fuel Naphthalene Content for

Condition 2

30. Dependence of Dome Radiation on Fuel Smoke Point for Condition 2

31. Correlation of Dome Radiation with Smoke point for Test Condition 2

32. Influence of Parametric Fuel Property Variations on Dome Radiation for

Condition 2

33. Correlation of Dome Radiatlon with Fuel Chemical Properties for Test

Condition 2

34. Influence of Operating Condition on Smoke Number for ERBS Fuel

35. Correlation of Liner Temperature Rise with Fuel Chemical Properties

for Test Condition 2

36. Influenc_ of Operating Condition on Particulate Diameter for ERBS Fuel

37. Influence of Operating Condition on Particulate Number Density for

ERBS Fuel

38. Soot Number Density Correlated with Smoke Number

39. Influence of Combustor Configuration on Exhaust Smoke Number i

40. Influence of Primary Zone Equivalence Ratio on Dome Radiation at Test

Condition 2

41. Influence of Combustor Configuration on Dome Radiation

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LIST OF TABLES

i. Test Fuels

2. Candidate Blending Components

3. Parametric Variations of Chemical Properties

4. Fuel Analysis Methods

5. Fuel Analyses

6. Combustor Open Area Distribution

7. Liner Effective Area Distribution

8. Primary Zone Equivalence Ratio Variation for Jet A

9. Fuel Atomization Levels

10. Fuel Temperature Influence on Atomization

ii. Fuel Nozzle Number Influence on Atomization

12. Fuel Nozzle Specification

13. Airflow Influence on Atomization

14. Test Facility Instrumentation

15. Emissions Analysis Instrumentation

16. Test Conditions

17. Measured or Derived Performance Parameters

18. Calculated Local Equivalence Ratios

19. Regression Analysis Results

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LIST OF SYMBOLS

A Fuel aromatic content, vol. pct

B Mass transfer number

CDA Effective area of liner hole

CP Gas specific heat

CPN2 Gaseous nitrogen specific heat

D Soot particle characteristic diameter

DP Fuel injector differential pressure

DPL Combustor liner differential pressure

EINOx Emission index for NOx

H Fuel hydrogen content, wt pct

I Scattered light intensity

I0 Incident light intensity at sample volume

k Gas thermal conductivity

L Length of combustion zone

N Fuel naphthalene content, vol pct

Soot particulate number density

n Complex refractive index

NN Fuel injector nozzle number

PB Barometric pressure

PF CombuRtor exit temperature pattern factor

-_ PHI Complex light acattering function

z

R Gas constant

R2 Square of regression correlation

t

SMD Fuel spray Sauter Mean Diameter

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SMD Critical SMD

c

SN SAE smoke number

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SP Fuel smoke point

TA Air temperature in combustor calibration tests

U Bulk gas velocity

u' Turbulence intensity, pct

WA Total airflow

WAL Airflow associated with primary zone sample

WCO2 Total metered carbon dioxide mass flow

We Weber number

We,c Critical Weber number

WF Fuel mass flow

WN2 Nitrogen mass flow

XCO2 Fractional molar concentration of CO2 in sample

x Light scattering siz_ parameter

e Light scattering angle

Wavelength of scattered light

Gas viscosity

PF Fuel density

¢ Gas density

g

_p Primary zone equivalence ratio

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,+)

SUMMARY

The ASTM "Standard Specification for Aviation Turbine Fuels" (ASTM

D-1655) defines acceptable limits for many properties of turbine engine

fuel for civilian use. F_I_ satisfying these limits will have characteristics acceptable to currenc gas turbine combustors. In particular,

desirable combustion characteristics are assured by bounding the aromatic

and naphthalenic hydrocarbon contents and the smoke point. Previous

studies have been conducted in an attempt to identify which of these

properties (or others) influence the performance, emissions and heat load

of the combustor. Fuel hydrogen content, which is not a specification

parameter, has been cited as a global indicator of fuel effects. These

earlier studies, however, did not purposefully emphasize the fuel chemical

properties; the combined influence of both physical and chemical properties

was likely observed. Additionally, the burners were not always representative of current aircraft practice and the range of fuel properties studied

was often limited.

In an attempt to rigorously study the fuel chemical property influence,

UTRC, under contract to NASA Lewis Research Center, has conducted an

experimental program using 25 test fuels. The burner was a 12.7-cm din

cylindrical device consisting of six sheet metal louvers. A single

pressure-atomizing injector and air swirler were centrally mounted within

the conical dome. Fuel physical properties were de-emphasized by using

fuel injectors which produced highly-atomized, and hence rapidly-vaporizing

sprays. A substantial fuel spray characterization effort was conducted to

allow selection of nozzles which assured that such sprays were achieved for

all fuels. The fuels were specified to cover the following wide ranges of

chemical properties: hydrogen, 9.1 to 15 (wt) pct; total aromatics, 0 to

I00 (vol) pct; and naphthalene, 0 to 30 (vol) pct. They included standard

fuels (e.g., Jet A, JP4), specialty products (e.g., decalin, xylene tower

bottoms) and special fuel blends. Included in this latter group were six,

4-component blends prepared to achieve parametric variations in fuel

hydrogen, total aromatics and naphthalene contents.

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

performed during which data were acquired for all 25 test fuels using a

single burner configuration. Second, configuration-effects tests were

performed using three fuels and two additional burner configurations which

produced either higher or lower primary zone equivalence ratios than

achieved with the fuel-effects configuration. Co_bustor heat load was

documented by full-hemispherical-sensing radiomecera mounted on the dome

J and by 39 liner thermocouples. Three narrow-angle radiometers mounted on i

the combustor case were used to sense shifts in the axial distribution of i

radiation. Arrays of thermocouples and sampling probes at the combustor !

exit were used to document the temperature pattern factor, and to acquire 1

gaseous and particulate specie samples. The characteristic particle size J

and number density of the exhaust soot on the combustor centerline were I

determined by an optical technique which interpreted scattered light i

signals according to Hie theory. All data were acquired at a single I

airflow condition which simulated high-power operation of a gas turbine i

combustor--namely, combustor pressure = 1.3 HPa and inlet air temperature = !

700E. Each test fuel was combusted at 3 fuel-air ratios which were i

specified to achieve combustor exit temperatures of 1246K, 1346K and 1473K. 1I

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Repetitive data points were acquired to determine the statistical

consistency of the measurements.

The combustor operated in s consistent manner for all tests. ComLustion efficiencies greater than 99.9 pct were always achieved; the exit

temperature pattern factor was tyFicslly less than 0.15. The output from

the case-mounted radiometers indicated that for each test condition, the

reaction zone structure was not significantly altered by any of the test

fuels. Hence all fuels were similarly atomized and distributed in the

burner. For every fuel, both exhaust smoke number and particle number

density decreased with increasing combustor fuel-air ratio (increasing

exit temperature), while the characteristic particle size remained constant. Indeed, the particle size was also independent of fuel properties;

the indicated size was always 0.22 _ 0.02 _m. The smoke number/number

density trends indicated that the soot oxidation mechanism dominated the

overall process of soot production. That is, despite an increasingly

fuel-rich primary zone at higher overall fuel-air ratios, lower levels of

exhaust soot were produced because of enhanced oxidation at higher exit

temperatures. These consistent trends also revealed a correlation between

smoke number and soot number density.

The principle influence of fuel chemical properties on the combustor

behavior were reflected by the radiation, liner temperature and exhaust

Smoke number (or equivalently, soot number density) data. The measured

dome radiative heat transfer rates appear to correlate well with fuel

hydrogen content. Used in this manner, however, the hydrogen content is a

global indicator of the fuel property influence since it is accompanied by

variations in total aromatics and naphthalenes. Results from tests with

fuels which offered parametric variations in hydrogen, total aromatics and

naphthalenes indicated that naphthalene content strongly influenced the

radiative heat load while parametric variations in total aromatics did not.

The hydrogen parametric test results indicated that, in a pure sense,

hydrogen content does not influence radiation load; only in a global sense

(i.e., with variations of hydrocarbon molecular structure) is a hydrogen

influence observed. Regression analyses werp performed on data from tests

with all fuels in an attempt to identify the individual influences of the

chemical properties. These analyses confirmed _he importance of

naphthalen_ content; a regression parameter containing both hydrogen and

naphthalene content tracked the data significantly be_ter than a parameter

containing b-drogen content alone. For the range of chemical properties

encompassed D2 Jet-A and ERBS, both the hydrogen and the naphthalene

content variations would contribute similarly to a variation in radiative

heat load. It was also observed that fuel smoke F)int correlated the data i

as well as the two-property par-me_er. Hence smoke point, an existing fuel

specification parameter, appears to be an adequate global indicator of fuel i

chemical property influences. Similar fuel effects were also observed _or

liner temperature rise and exhaust smoke number. 1

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The configuration-effects test results indicated that the fuel concentration pattern in the primary zone of the combustor strongly influenced i

the soot levels produced, and therefore also the radiative heat load. I

Since the fuel oxidiation is controlled by a turbulent diffusion flame t!

structure, the global value of primary zone equivalence ratio (¢) does not I

always properly represent the important features of this region, p Data

indicated that particulate radiation heat loads on the combu_tor dome could

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be constant despite ¢_ values ranging from 1.2 to 1.6 if fuel concentration

patterns were invaria_t.

xi
Aviation-Fuel Property Effects on Combustion

SECTION I - INTRODUCTIC

Aviation gas turbine engines combust hish quality fuel. The principle

fuels for either commercial service, Jet A, or for military service, JP4

and JP5, were developcd to possess excellent combustion characteristics

while offering appropriate considerations for ease of ignition, safe

handling and low-temperature fluidity. These fuels have attractive energy

densities, atomize and vaporize readily, and burn completely in the time

and temperature environment found ;u gas turbine combustors. The jet fuel

specification assures obtaining this performance by controlling several key

physical and chemical properties. The original specification was established to obtain these features while assuring adequate supplies of

reasonably-priced fuel derived from domestic petroleum reserves. The

availability of domestic crude oil has continuously decreased in recent

time, however, forcing an increase in the quantity of petroleum imported to

the U.S. In the last decade, the cost and availability of such imports has

not been stablp. The oii embargo of the early 1970's threatened adequate

availability of petroleum in the U.S. and the subsequent production/

pricing practices of OPEC countries have caused dramatic increases in the

cost of petroleum products. Gas turbine users have experienced more zhan

a four-fold increase in unit fuel costs.

Substantial increases in gas turbine engine operating expenses have

placed a premium on developing aircraft gas turbine systems which can

offset the fuel cost burden. Two basic, although not mutually exclusive,

approaches could l e pursued: develop more fuel efficient systems or develop

more fuel tolerant systems. The former approach is obvious and is likely a

desirable goal for any level of fuel cost. The latter approach would

attempt to use less costly feel without sacrificing the performance or

endurance of the gas turbine engine. It is possible that existing systems,

with or without minor retrofit, could be qualified on less expensi_-e

fuels. Of course, the fuel cost is not represented by the fuel production

cost alone. Fuel handling requirements, fuel system alterations, airframe

modifications and gas turbine hot section (combustor and turbine)

deterioration associated with the use of an alternative fuel represent

costs which must also be considered.

One part of an overall evaluation of a fuel tolerant system is an

investigation of the influence of fuel properties on the performance, emissions and heat rejection of a gas turbine combustor. Since 1975 numerous

investigations have been conducted (Refs. I through II) to quantify such

influences. The studies have used laboratory model combustors, full engine

hardware, actual fuel, hydrocarbon specialty products (i.e., solvents) and I

blends of these two material classes. Such efforts have identified areas J

which would likely be affected by changing fuel properties. For example, I

_iner temperatures, exhau6t smoke emissions and low power (idle) emissions I

are three parameters often cited as being influenced by fuel properties. I

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Unfortunately, the fuel variation_ studied have resulted in simultaneous changes in the physical and chemical properties. These two types of

properties ould be expected to influence different processes within a gas

turbine combustor. Physical properties (specific gravity, viscosity and

surface tension) would predominantly affect the fuel atomization process,

and hence alter the distribution and rate of vaporization of the fuel.

Chemical properties (hydrogen, aromatic or naphthalene content) would

influence the fuel oxidation process, altering the type, concentration and

rate of consumption of chemical species within and exiting the combustor.

Depending on the dominant mechanisms withiv the burner, changes in the

fuel, may or may not produce an interpretable change in a parameter of

interest.

For example, if in an attempt to investigate high fuel aromatic

content, the surface tension also significantly increased, it may not be

possible to separate the multiple effects of these changes and correctly

interpret the data. That is, high aromatic content alone may promote

greater .oncentrations of carbon and hence higher liner temperatures

because of increased flame radiation. Alternatively, the increased surface

tension could degrade the fuel atomization and distribution, producing

locally fuel-rich regions which could similarly could result in high liner

temperatures. Clearly there was a need for an investigation which

attempted to separate the influence of fuel physical property variations

from those of chemical property variations.

United Technologies Research Center has conducted an experimental

program under contract to NASA-Lewis Research Center (NA53-23!67) to investigate the influence of fuel chemical properties on the performance, emissions, and heat load on a gas turbine combustor. Fuel physical properties

weze de-emphasized by using injectors capable of achieving highly-atomized, i

and hence rapidly-vaporizing fuel sprays for each of twenty-five test I

fuels. The fuels were specified to cover wide ranges in fuel hydrogen,

total aromatic and naphthalene content; a limited number of fuels were

blended to achieve parametric variations of these properties. Two types of

combustion tests were performed. First, fuel-effects combustion tests were

performed with a constant burner design at a simulated high-power gas

turbine operating condition using all 25 test fuels. Second,

configuration-effects combustion tests were performed with burners designed

to produce either higher or lower primary zone equivalence ratios than the

baseline design. Ccqnbuator airflow calibration and fuel spray

characterization studies supplemented the combustion tests.

This document reports the results of this investigation. Section II

describes the selection and analysis of the test fuels, while the design

and calibration of the combustor is detailed in Section IIl. The extensive fuel spray characterization effort is described in Section IV.

Sections V and VI describe the combustor test facility and instrumentation,

and the test condition, procedures and data handling, respectively. The

results of the fuel-property-effects testing are presented and discussed in

Section VII, with configuration-effects results contaived in Section Vlll.

Conclusions and recommendations are listed in Section IX.

2
SECTION II TEST FUELS

The ASTM standard specification (ASTM D-1655) defines acceptable

limits for many properties of turbine engine fuel for civilian use. Fuels

satisfying these limits will have fluidity, compatibility, cleanliness,

stability, volatility and combustability characteristics acceptable to current gas turbine combustors. Fuel combustability is assured by bounding

the aromatic and naphthalene contents and the smoke point. Hydrogen

content is not a fuel specification paramter. However, many previous

studies have determiu,.d that the results of changing fuel chemical properties correlate with the fuel hydrogen content. Therefore, in this investigation attention was focused on the fuel chemical composition as represented by the hydrogen, total aromatics and naphthalene contents. The smoke

point was not considered to be a fundamental parameter but rather resulted

from tl.ehydrocarbon mix of the fuel. It m_y therefore be a desirable

global indicator of the fuel chemical properties. Indeed, the three

chemical property classes-hydrogen, total aromatics and naphthalenes--wEre

also gross parameters of the fuel. Obviously, hydrogen content alone does

not specify the type of hydrocarbon molecules contained in the fuel.

Similarly, "total aromatics" and "naphthalenes" do not pinpoint the type of

aromatics, etc. As reflected by the AS,_M specification it has been assumed

that the three major property classifications selected dominate the

combustion characteristics and hence are the proper ones for evaluation.

The twenty-five test fuels were selected to provide wide ranges of

variation in these properites, with hydrogen contents from 9.1 to 15.0 (wt)

percent, total aromatics contents from 0.0 to I00.0 (vol) percent, and

naphthalene contents from 0.0 to 29.7 (vol) percent. Table I provides a

list of the fuels and these chemical properties as determined from analyses

described below. This section of the report describes the test fuels and

presents the results of extensive analyses performed on each.

Fuel Description

The test fuels could be divided into three general categories: common

fuels, specialty products and blends of these two categories. The common

fuels and speciality products were specified by NASA; UTRC collaborated

with NASA to specify the blends.

Common Fuels

Four of the test fuels were products commonly used in gas turbine

combustors: Jet A, JP4, JP5 and JP7. Each of these was a high-quality,

petroleum-derived fuel produced in accordance with ASTH and USAF specifications. Four additional fuels within this category were: ERBS, JP4-S,

JP4-A and DF2. ERBS (Experimental Referee Broad Specification) fuel

evolved from a NASA-directed workshop on alternative hydrocarbon fuels

(Ref. II). Unlike most fuel specifications, which place upper limits on

certain chemical properties, a single level (and tolerance) of hydrogen

content is specified for ERBS. This approach minimizes the chemical

property variation of subsequent batches of ERBS production; it has become

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a stsndard fuel for NASA-sponsored fuel effects investigations. JP4-S was

a JP4 specification product derived from oil shale resources. JP4-A, like

JP4, was a petroleum-derived fuel satisfying the USAF specification, but

it had a high aromatic content. That i6, while most JP4 fuel contains 16

to 18 (vol) percent aromatics, JP4-A contained 23 (vol) percent which is

n-_r the specification maximum of 25 (vol) percent. The DF2 fuel was a

better quality No. 2 fuel oil.

Specialty Products

In order to extend the ranges of _he chemical properties of interest,

six of the test fuels were specialty products: decalin, tetralin, xylene

tower bottoms (XTB), blending stock (BLS), Gulf Nineral Seal Oil (GMSO) and

UTRCI. Many of these products have also been used in other combustor fuel

effects evaluations. Both decalin and tetralin were pure, double ring

hydrocarbon solvents procurred from E. I. duPont de Nemours. Decalin is a

product of the complete hydrogenation of naphthalene to naphthene.

Tetralin results from partial hydrogenation of naphthalene to result in a

f,sed, double 6-carbon ring structure, with one ring being saturated and

the other unsaturated. Hence while decalin retains no aromatic quality,

chemical analysis would classify tetralin as fully aromatic. XTB consisted

of various single-ring aromatic compounds (a)kylbenzenes) while GHS0 was a

relatively high final boiling point oil consisting mostly of normal and

monocyclic paraffins. BLS was a mixture of XTB and a gas oil that NASA had

obtained to use for modification of fuel properties, and contained substantial single-ring and double-ring aromatic compounds. UTRCI was a commercial solvent, EXXON Isopar M, chosen by UTRC to meet the NASA requirements

for a high hydrogen content fuel void of aromatic compounds.

Fuel Blends

Eleven of the test fuels were blends of common fuels and specialty

products. Of these, five were prepared to provide chemical property levels

between those offered by other test fuels. For these, as for the common

fuels and specialty products, simultaneous variation in hydrogen, total

aromatics and naphthalene contents resulted. Six of the blends were specially prepared, however, to avoid this multiple variation. That is, two

fuels were blended to achieve parametric variations in either hydrogen,

total aromatics or naphthalene content.

The five fuels prepared to provide blends with additional chemical

properties were: AFAPL2, AFAPL6, ERBLSI, ERBLS2, ERBLS3. The first two

fuels were supplied by the Air Force Aero Propulsion Laboratory, WPAFB, and i

consisted of JP4, XTB and A-400 solvent and JPS, DF2 and A-400 solvent,

respectively. (A400 is an aromatic solvent containing approximately 50

percent naphthalenes.) Both of these fuels have been used in fuel effects

evaluations of gas turbine afterburners (Ref. i3). The latter three blends tl

were diffent volume mixtures of ERBS and BLS; these fuels were blended by )i

UTRC. i

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It was desired to evaluate test fuels which allowed parametric varia- i

tions of fuel hydrogen, total aromatics and naphthalene contents. Such i!

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variations were not easily achieved because alterations in any one property

would normally affect one or both of the other chemical classes. Hence

parametric variation of the properties of interest were obtained by substituting one type of compound for another from the same general class. For

example, use of decalin in lieu of UTRCI (i.e., EXXON Isopar M) would not

change _he total aromatics or naphthalene content of a blend, but would

reduce the hydrogen content. The mix of saturated hydrocarbons would be

altered, however, with a greater fraction of cycloparaffins being present

with use of decalin, and a greater fraction of normal paraffins present

with use of UTRC1. Only by careful selection of the fuel blend components

were parametric variations achieved.

The specification for the parametric variation blends resulted from au

extensive computer screening exercise. That is, recognizing that such

fuels would result only from blends of several components, a computer

program was written which, given the chemical properties of potential components, evaluated all possible combinations. Ten potential blending

components were identified, with samples of each analyzed to provide

consistent chemical property data, see Table 2. (Each of these components

has been previously described except for the Methyl-naphthalene fraction.

This solvent is a fully aromatic liquid with a very high naphthalene

conten_.) The final blend was limited to four components. Goal levels for

hydrogen, total aromatics and n_phthalenes (and allowable tolerances) were

input to the computer code which analyzed 4-component permutations of the

ten candidates. The component volume fractions were incremented by 5

percent in successive evaluations, resulting in approximately 372,000

"computer blends".

Three-point parametric variations in hydrogen, total aromatics and

naphthalenes contents were sought, based upon two fuel blends departing

from a connnonfuel (e.g., ERBS). The results of the computer blending i

exercise indicated that meaningful three-point variations could not be

achieved for hydrogen or aromatics, however, because the constraints

imposed by the other two properties prohibited significant independent

variation. As an alternative, a pair of 2-point variations in hydrogen and

total aromatics (i.e., two base fuels) were determined. The compositions

of the parametric blends are listed in Table 3 with the results of analyses

to determine the blend chemical properties. The parametric variations

achieved were identical to those predicted by the computer blending code

(within the chemical analysis uncertainties) and represented the greatest

variation that could be expected using the ten candidate components.

The three ERBS/BLS and six parametric blends were prepared by UTRC.

Th_ volume fraction specifications were translated to mass fractions and a

shipping scale used to weigh the quantity of each component pumped into s

1000 liter mixing tank. The entire batch of each blend was mixed by i

pumping the fuel out of one end of the tank and into the other; the circulation time was sufficient to displace the blend volume at least ten times.

The fuel was subsequently pumped from the mixing tank into drum_; the

mixing tank was then cleansed with the major constituent of the next blend

to be prepared.

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Fuel Analysis

A sample of each test fuel was analyzed by Southwest Research Institute in accordance with the properties and procedures indicated in Table 4.

The results of these analyses are presented in Table 5. The levels of

total aromatics and naphthalenes presented for any fuel (or blending

component) were obtained from mass spectrometric analysis. All

hydrocarbons contained in the aromatic fractlon of the sample contributed

to the "total aromatics" level. The naphthalene compounds were assumed to

include the acenaphthenes (C Ha ..) and acenaphthalene (C H_ ,,) n n-l_ . Lnhydrocarbons. The volume fraction values were determlned _rom _e reported

mass fraction data and the following assigned specific gravity values:

Hydrocarbon Type Specific Gravity

normal-paraffins 0.75

cyclo-paraffins 0.81

alkylbenzenes 0.87

indans and tetralins 0.93

indenes 1.00

naphthalenes 1.00

tricyclic aromatlcs 1.28

The type of hydrocarbon species in the fuel was independently

determined from more than one analysis. The m_ss spectrometric analysis

(ASTH D2425) separated the fuel into twelve classes while the fluorescent

indicator adsorption (FIA, ASTH D1319) technique reported only on three

general classes (saturates, olefins, total aromatics). The FIA was

supplemented with the ultraviolet spectrophotometric technique (ASTM 1840)

to determine naphthalene content. A comparison of the total aromatics and i

naphthalene contents obcained by two techniques is shown in Figs. I and 2,

respectively. The mass spectrometry and FIA results for aromatics agreed

remarkably well considering the wide range covered and the general

acknowledgement that the FIA technique can be inaccurate for high aromatic

levels. The two techniques did not correlate well only for BLS. The

agreement with naphthalene analyses was poorer, with a substantial

underprediction by the UV technique. This result was not surprising a_

this method is strictly applicable to fuels containing only up to 5 percent _

naphthalene; reasonable agreement was obtaJted to this level. The data in

Fig. 2 again indicated that an analysis of BLS was questionable. In

particular, it appeared that the mass spectrometric data were in error i

because the naphthalene content measured was less than obtained for the i

ER3LS3 blend (41 pct ERBS, 59 pct BLS). i+

The BLS analysis error was probably introduced by the the saturates- !

aromatics separation step of the mass spectrometric analysis. That is, the !

technqiue requires that the fuel sample be chemically separated into these I

two fractions, with each one being individually analyzed. The properties I

of the entire sample are determined by numerically weighting the fractional I

analysis by the percent of total mass represented by the fraction. After _

separation, the mass of the fractions ought to be equal to the original J!
sample mass. For most fuels, this conservation was obtained to over 98

percent. For BLS however the sum equaled only 85 percent. Clearly, the

particular hydrocarbon mix of BLF did not separate into the saturatesaromatics fractions well and some compounds were lost to the separation

solvent. This problem really stemmed from attempting to use analysis

techniques beyond their intended range of applicability; however, efficient

alternatives do not exist.

The levels of aromatics and napthalenes for BLS were determined from

the values obtained for ERBS, and the three ERBS-BLS blends. Since the

s_me fuels were used to prepare the blends, their properties ought to

represent linear combinations of ERBS and BLS values. The property values

for BLS were calculated from these blends, and it was concluded that the

appropriate levels of aromatics and napthalenes for BLS were 76.0 and 29.7

(vol) percent, respectively. These levels, shown as corrected levels on

Figs. I and 2, were used in test data analysis.

r
SECTION ili - GENERIC GAS TURBINE COMBUSTOR

A model combustor was designed, fabricated and tested, which embodied

the features of a gas turbine burner. This section of the report describes

both the burner, specifying its geometry and expected performance, and

calibration tests which were performed to document the burner airflow distribution.

Combustor Description

A combustor embodying the features of a gas turbine burner was

designed and labricated. That is, it was a high heat release device, with

a strong swirling-recirculating flow structure at the front end (i.e.,

primary zone) followed by penetrating jets of air to gradually reduce the

local fuel-air ratio, and hence gas temperature, to levels acceptable to a

turbine. Design guidelines were established for both the geometry and performance of the burner. These were:

Geometry: (I) cylindrical burner with maximum axisymmetry

(2) burner diameter between I0 and 15 cm

(3) burner must permit meaningful changes in the

primary zone fuel-air ratio

Performance: (I) combustion efficiency > 99 percent

(2) total pressure loss < 8 percent

(3) combustor exit pattern factor < 0.3

(4) liner temperatures consistent with current

aircraft practice

The primary variable investigated in the program was fuel chemical i

properties; a single airflow test condition was used. Hence, the perfor- i

mance guidelines applied only ;o the following simulated high-power

condition:

combustor upstream pressure: 1.3 MPa

combustor inlet temperature: 700K

combustor overall fuel-air ratio: 0.015, 0.018, 0.022

Strictly, the fuel-air ratios applied only for operation on Jet A fuel; for

other fuels, the fuel-air ratios were to be specified at she levels

required to produce ideal combustor exit temperatures equal to those for

Jet A.

/

Considerations of these guidelines led to specifying a louver-cooled,

cylindrical burner with s n inside diameter of 12.7 em (Fig. 3). It consisted of a dome constructed from a frustrum of a 90 deg cone and six, 1

conventional sheet-metal louvers; the overall length was 41.1 cm. A flange I

on the dome was provided to mount a central fuel injector-swirler combination; the dome also had penetrations for a spark igniter and two transpiration radiometLrs (See Section V). The dome cooling air was admitted

through four rows of equally-spaced holes, and each louver was fed by a
ring of equally-spaced holes. Four of the louvers contained six large

holes to admit combustion air to the burner; these holes represented the

greatest deviation from axisymmetry. The number and diameter of all

combustor holes are listed in Table 6.

The combustor liner described above was the baseline configuration

used in the fuel-effects combustion tests. A limited number of tests were

conducted to determine the influence of a different primary zone

equivalence ratio for a constant overall fuel-air ratio. These tests

labeled "Configuration-Effects" tests, were accomplished by using either of

two modifications to this baseline burner. For tests in which a leaner

primary zone was desired, the combustion aiz holes in the first louver were

opened to a diameter of 18.0 mm while the holes in louver 5 were blocked.

This alteration kept the total open area constant while permitting

additional air to be entrained into the primary zone. For tests in which a

richer primary zone was desired, the diameter of the holes in the first

louver was reduced to 6.4 mm while the holes in louver 5 were opened to

14.2 mm. Again, the total open area remained constant but a reduced

airflow was available to the primary zone. The level of airflow associated

with the primary zone was determined by a carbon dioxide tracer technique

for the baseline configuration and extended to apply to the two modified

burners. This technique and the results are described below in the

subsection entitled Combustion Calibration.

The twenty five test fuels provided a wide range of both chemical and

physical properties. In order to eliminate the influence of the physical

properties on combustion, highly-atomized, and hence rapidly-vaporizing,

fuel sprays had to be achieved. Recognizing that atomization quality

deterioration can be offset by proper nozzle selection (i.e., capacity),

a family of fuel injectors was sought. In particular, pressure atomizing

injectors produced by Hago Manufacturing Inc. were used (Fig. 4a). All

injectors produced hollow cone sprays with a rated included cone angle of

80 deg. The nozzle size used with each test fuel w&_ determined from the

spray characterization data described in Section IV.

An air swirler encircling the fuel _ zzle provided the swirl necessary to assure stable combustor operation. The device enhanced fuel-sir

mixing and distribution and established the recirculating primary zone

flowfield. The swirler used was a commercially available device developed

by Pratt & Whitney Aircraft for the JT 12 combustor (Fig. 4b). It

embodies both the primary air swirler and the nozzle nut. The swirlerinjector combination mounted in a flange on the dome of the combustor; an

annular clamp ring assured proper positioning and sealing.

The performance of the burner was evaluated to assure operation within

the design guidelines. As originally planned, a combustor total airflow of

2.0 kg/s would be used, which would produce a liner pressure loss of 2.0

pct and a reference velocity (based on the combustor diameter and approach

airflow density) of 25.4 m/s. (The actual airflow was reduced during

shakedown testing to 1.8 m/s because of test facility limitations, which

thereby reduced these levels to 1.6 percent and 23 m/s, respectivel>.) The

stability and combustion efficiency characteristics were predicted

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following the techniques of Odgers and Carrier (Ref. 14) with the

efficiency re-affirmed by considerin_ the caoon monoxide emissions

according to Mellor (Ref. 15). In all cabes, the burner was predicted to

be very stable and to operate at combustion efficiencies greater than 99

percent. The level of penetration of the combustion air jets was also

evaluated using the correlation presented by Abromovich (Ref. 16).

Predicted penetration distances were similar to those achieved in a

comparative commercial gas turbine combustor, indicating that a vigorous

mixing of these jets and the bulk flow was likely; a low pattern factor

was expected.

Combustor Calibration

Combustor calibration tests were performed to document the distribution of liner airflow. Data were acquired to calculate both the effective

area (i.e., discharge coefficient * geometric area, CDA) of the holes at

each axial station and the percentage of total airflow involved with the

primary zone. This information was necessary to describe the gross

variations in fuel-air ratio occurring within the burner. In particular,

the primary-zone airflow split was necessary to calculate the equivalence

ratio in this critical section of the combustor.

Effective Area Tests

As a first step in defining the combustor airflow distributio., tne

effective area of the liner holes at each axial section--i.e., dome, louver

I cooling, louver I combustion air, etc--was determined. These data were

obtained from tests performed in the UTRC Jet Burner Test Stand (JBTS)

using the setup depicted in Fig. 5. All liner holes except those at the

position of interest were taped closed. The liner was mounted in the test i

section, with this assembly mated to the normal upstream facility

components (see Section V for a complete facility description). The liner

exit was completely open to the test cell. High pressure, dry _ir was

supplied to the JBTS and metered with a venturi sized to operate choked.

The airflow pressure and temperature upstream and pressure at the throat of

the venturi were measured. A board of water manometers was used to record

the pressure drop across the liner. Three levels of airflow were used to

acquire data at liner pressure losses of approximately I, 2, and 3 percent.

The effective area was calculated for each airflow according to:

WA

CDA = [2,(PB+DPL).DPL/R/TA]. 1⁄2

where WA = air mass flow

DPL = measured liner differential pressure

PB = barometric pressure I

TA = air temperature I

R = gas constant

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The three values of CDA were plotted, with the value corresponding to a

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combustor-equivalent flow parameter identified. In fact, since the combustot airflow Mach number was low for all tests, the effective area did not

significantly vary with airflow rate. The selected effective areas are

listed in Table 7. Also shown are levels obtained in separate tests fo:

the swirler CDA and for the total liner. The sum of the individual station

CDA matched the liner total to within the estimated uncertainty of _ 3 pct.

The sectional values were adjusted to match the measured total liner CDA as

indicated in the table.

Primary Airflow Study

The combustor primary zone is a region of high heat release which is

largely responsible for burner stability, efficiency and exhaust emissions.

The effectiveness of this zone is closely associated with the primary zone

equivalence ratio, __. However, calculation of _ is not straight-f_rward

as the course of som_ airflows which penetrate thePliner is unknown. That

is, while the airflows admitted by the swirler and dome would clearly

participate in this zone, it was not certain what percentage of the louver

I combustion air would be entrained into the recirculating flow. In an

attempt to clarify this situation, a carbon dioxide (CO2) tracer gas was

used to identify the primary zone flow.

The primary zone airflow tests used a test setup similar to that

described above for CDA determination. That is, a metered airflow was

delivered to a combustor liner mounted in the test section; the combustor

exit was open to the test cell. All liner holes were open and a normal

fuel nozzle-swirler combination was mounted on the dome. The fuel nozzle

was a Hago device which haa been modified by opening the internal flow

passages and adding a l-cm long, closed-end extension tube on its face.

The tube had eight orifices distributed along its surface which permitted

injection of COp gas into the surrounding swirling airflow. During

testing, the to[al airflow was set to match the flow parameter for the

combustion tests, and a metered flow of CO2 was injected into the primary

zone. Gas samples were extracted using a multiple-point probe constructed

from thirteen, 3.2 nnn OD, equal length tubes (Fig. 6). The tubes were

manifolded into two sets: Set one included the outer six and the central

tube; set two contained the six tubes on the inner circle. The position of

the probe assembly was identified by the axial and angular positions of the

probe tip. Samples were obtained at axial intervals of 1.2 cm at the head

end of the combustor, and for angular orientations which placed the sample

tubes in line with or between the six, large combustion air holes in the

first louver. Samples from either set were analyzed for CO2 concentrations

using a Beckman NDIR analyzer. Airflow splits (i.e., percent of the total i

airflow) were calculated from the local CO2 concentration according to: i

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WA WA XCO2 I

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where WAL - local air mass flow associated with sample i

WA = total metered air massflow

WCO 2 = total metered C02 mass flow i

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XCO. = fractional molar concentration of CO2 in sample

K Z constant accounting for species molecular weights

Since only the total flowrate of air and CO_ are metered, this tracer gas • ° _ • • •

approach yielded quantitative information only if the region being

investigated was well-mixed. A data consistency test was performed using a

liner with all holes closed except those on the dome. The CO2 concentration at the combustor exit was uniform, and its value corresponded to

fully-mixed CO2 and air at the metered flowrates.

The data acquired from tests of the total combustor are depicted in

Fig. 7. Data for both probe sets _nd for probe orientations between an_

inline with the louver 1 combustion air holes are presented. The data

indicated a relatively well-mixed primary zone (i.e., region upstream of

the combustion air holes), with little distinction in data acquired for

either probe set or azimuthal orientation. This homogeneous character

permitted meaningful calcuation of the airflo_ split. Approximately 19.5

percent of the total airflow was determined to be involved in the primary

flowfield.

Also shown in the figure are the cumulative effective open areas of

the llner. The sum of the swirler and dome cooling CDA represented 16.3

percent of the liner total, indicating that airflow from another source had

heel, recirculated upstream. It was assumed that all of this excess originated from the louver 1 combustion air holes; the calculated entrainment

level was 26 percent of this flow.

The CO. tracer study indicated that 19.5 percent of the total airflow

participate_ in the primary zone flowfield. Hence, the ¢ value would be

5.1 times the overall equivalence ratio, for the baselinePcombustor.

Variations in _ applicable to the combustors used in the Configuration

Effects Tests a_e depicted in Tmble 8 (the values are those associated with

Jet A). For the baseline configuration, which was exclusively used in the

fuel-effects tests, __ ranged between 1.2 and 1.7. For the configurationeffects tests, the combustion air holes in louver 1 and 5 were modified to

produce leaner and richer primary zones (see Description of Combustor).

Application of the above 26 percent entrainment level led to the airflow

splits and __ variations presented in the table. As can be seen, the three

configurations provided three levels of ¢ for a constant overall fuel-air

ratio, and at least two levels of overallPfuel-air ratio for the same _p.

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SECTION IV - FUEL SPRAY CHARACTERIZATION AND INJECTOR SELECTION

The principle objective of this program was to determine the _nfluence

of fuel chemical properties on the operation of a gas turbine combustor.

Fuel physical properties were de-emphasized by producing finely-atomized,

and hence rapidly-vaporizing, sprays for all fuels. This section of the

report describes the nozzle characterization effort necessary to select

injector1_which met the atomization goal.

Atomization Goal

The twenty-five test fuels provided wide ranges in both chemical and

physical properties. Variations in either could influence the burner

characteristics. Fuel chemical properties would primarily affect the type

and concentration of hydrocarbon species within the burner. For example,

hydrogen-deficient fuels might produce greater carbon concentrations,

resulting in higher radiation heat loads (and subsequently higher liner

temperatures). Fuel physical properties would primarily affect the level

of atomization. That is, fuels with disadvantageous physical properties--

high levels of viscosity or surface tension--would tend to form coarse

sprays, with these relatively larger droplets penetrating deeper into the

airflow and surviving for significantly longer time periods. Clearly the

size, location and intensity of the combustion zone would respond to such

fuel distribution alterations, and consequently the combuetor characteristics would also change. In order to isolate chemical property influences,

the processes dependent on physical properties must be minimized. Only by

achieving highly-atomized and hence rapidly-vaporizing sprays can this goal

be satisfied.

Ballal and Lefebvre (Ref. 17) analytically considered the influence of

fuel chemical and physical properties on the combustion efficiency of a gas

turbine combustor. Limiting cases were identified where the heat release

rate was dominated by either chemical reaction, mixing or fuel

vaporization. Mixing-controlled situations were readily dismissed by the

authors by stating that "there exists no evidence to suggest that mixing

rates are ever limiting to the combustion efficiency of gas turbine combustors." l]ence great attention was given to defining system

_haracteristics which separated reaction-controlled and vaporizationcontrolled operation. In particular, a vaporizing fuel spray charecterized

by a Sauter Mean Diameter (SMD) droplet was analyzed. Convective heat and

mass transfer was included by assuming that the droplets do not respond to

the turbulent velocity fluctuations of the airflow. A critical SMD was

identified (SMD); for SMD > SMD fuel vaporization would control the heat

release : c c' _i

SMDc _ 2.4 * -- . k__ . In (I+B) * L * 1

Of Cp _ I

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where _ = gas density

_ = fuel density

= gas ghermal conductivity

CP = gas specific heat

B = mass transfer number

L = length of combustion zone

u' = turbJlence intensity, pct

U = bulk gas velocity

= gas kinematic viscosity

Large values of SMD would indicate that the fu_l properties (fuel volatility through B) andCflow condition kconvective >.at transfer through u')

were favorable to vaporization--that is, a large 2._ could be tolerated

without becoming vaporization controlled. Longer combusticn zones or

greater residence times, L/U would also increase SMJ . C

The critical droplet size to avoid vaporization control was evaluated

for the combustor used in this test program. In particular, the SMD value

sought was to assure rapid vaporization within the combustor primaryCzone

which, based upon the test conditions and flow splits, had a r_sidence time

of approximately 5 ms. Calculations indicated that for Jet b ael, a 20

percent turbulence intensity, and a droplet lifetime half the primary zone

residence time, SM]) = 52 _m. That is, a Jet A spray with a SMD < 52 _m ¢ .

would vaporize sufficiently fast so as not to limit the heal.release rate.

The least volatile test fuel to be tested had distillat:#n cilaracteristics

similar to a No. 2 oil. For the same conditions as described above, the

critical diameter was calculated to be SMI) = 45 _m.

C

A second analysis of fuel vaporization was conducted using the UTRC

Spray Vaporization Computer Program. This code employs an axisy_nnetric

stream tube calculation technique, with fuel vapori:ation and droplet-gasphase mixing modeled through consideration of convective and diffusive exchange of mass, momentum and energs. Initial levels of the air pressure,

temperature and velocity and fuel temperature, velocity and droplet size

were specified. The multi-component nature of the fuel is treated

followil,g the technique of Cox (Ref. 18) by use of the fuel distillation

curve. The governing equations are solved by a forward marching, finitedifference procedure to provide a streamwise evolution of the two-phase

flow properties.

The calculated droplet lifetimes, i.e., complete vaporization, for

specified initial droplet diameters of Jet A or No. 2 oil are presented in

Fig. 8. The results were obtained for the same operating condition of the

primary zone as for the Balls! analysis. Again the convective heat and

mass transfer was represented by the inability _f the droplet to respond to

turbulent velocity fluctuations. To achieve complete vaporization within !

half the primary zone residence time, i.e., within 2.5 ms, the SMI) of the 1

Jet A spray could approach 65 _m while for Xe. 2 oil the spray must be 1

limited to SM]) < 56 _m. These results were similar to those aci,ieved in j

the preceeding analysis and t_terefore confirmed the approximate level of i

atomization required to eliminate fuel physical property influences. In I

principle, the finest level of atomization, i.e., smalie_t droplets, ought i

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to be sought to truly minimize this influence. This extreme would have

imposed unacceptable demands on the test program--excessive fuel pressures

and/or nozzle substitution for every 2uel, for each of three fuel flowrates, would have been required. These considerations and the results of

the vaporization analyses led to specifying a spray atomization goal of: 35

< SHD < 45 Vm for all fuels at the median fuel flowrate. The selection of

fuel nozzles to _chieve this goal was the objective of the injector

characterization effort.

Fuel Spray Characterization

In order to assure meeting the atomization goal, the fuel spray formed

by each of the 25 test fuels was experimentally characterized. Spray SMD

and cone angle were determined for all fuels with a single nozzle, with

additional tests performed to quantify the influence of nozzle size (capacity), fuel temperature and swirler airflow. As described in Section iii

all fuel nozzles were pressure-atomizing devices produced by Hago Manufacturing Inc., which were rated to produce hollow cone sprays with ii_cluded

cone angles of 80 deg.

Spray Characterization Facility

The characterization of the fuel sprays was performed in the UTRC

Ambient Pressure Fuel Spray Facility located in the Jet Burner Test Stand.

This facility, which is routinely used to determine spray patterns and

droplet size distributions, was designed to operate over wide ranges of

fuel and air flowrates. Fuel could be delivered from either a large capacity Jet A supply or a smaller (approximately 20 liter) hatch supply. The

system also provides for fuel temperature conditioning (heating or

cooling). The pertinent components used for the present study are depicted i

in Fig. 9. The fuel nozzle was mounted with the combustor air swirler on a i

canister which acted as a plenum for swirler airflow; swirler airflow

was used only for a limited number of tests to document its influence on

the fuel spray. Either the Jet A or the batch fuel system could be

selected by activating a 3-way valve; each system contained the appropriate

components to pump the fuel and regulate its flowrate. The fuel delivered

to the nozzle was metered by a Micromotion mass flowmeter. Fuel pressure

and temperature were measured at the injector. A calibrated venturi was

used to meter the swirler airflow, with appropriate pressure and

temperatures at the venturi measured.

The fuel spray pattern and droplet distribution _ere documented, i

Photographic _ecords of the spray were obtained to determine the included t

" cone angle. A high power General Radio Strobolume illuminated the spray !

with a I0 ms light pulse substantially freezing the droplet motion, i

• Polaroid film was used. A Malvern Model STI800 Particle Size Analyzer was I

used to measure the droplet size distribution in a plane 6.4 cm downstream I

from the injector, This instrument is based on Fraunnofer diffraction of a I

par_llel beam of monochromatic light by moving or stationary particles. A i

He-Ne laser beam traversed the spray diameter with the diffracted light I

sensed on a 30-element photoelectric detector. The d_ta were acquired 1

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using a 300-mm focal length collecting lens which permitted detection of

droplet sizes between 6 and 560 _m. The photocells were scanned 200 times

(approximately 2.6 sec) to acquire a stati_tically meaningful average for

each data point. A dedicated mini-computer stored the diffracted light

data and, upon request, executed an analytical progrmn to interpret these

signals in terms of a Rosin-Rammler droplet distribution and calculate a

spray SMD.

Test Plan and Procedures

Four sets of fuel spray characterization tests were performed:

(I) All fuels were sprayed at three fuel flowrates using one injector.

The injector was a Hago No. 35 nozzle, where the nozzle number (DIN)

indicated the rated volume flow of No. 2 oil (gal/hr) at a dfferential

pressure of 0.69 MPa (I00 paid). The same fuel mass flowrates were

u_ed for all fuels, being 118, 133 and 162 kg/hr. These levels were

approximately the flows required for Jet A at the combustor test

condition.

(2) Two fuels were sprayed at three fuel temperature levels using one

injector. The two fuels were Jet A and tetralin, at temperature

levels of 290, 311 and 328K. ANN = 35 nozzle was used.

(3) Two fuels were sprayed at multiple flowrates through each of three

injectors. The two fuels, Jet A and tetralin, represented a baseline

and an extreme variation in physical properties. Nozzle sizes

included NN = 20, 30 and 35. The five flowrates included the three

above and, for the smallest nozzle, two lower rates of 83 and 96

kg/hr.

(4) Two fuels were sprayed using one injector and two levels of swirler

airflow. The two fuels were Jet A and tetralin and the nozzle was a i

NN = 35 device. The two airflow levels were characterized by the

differential air pressure established across the swirler (DPSW). Data

were _cquired for DPSW = 4.9 and 26.2 kPa, which corresponded to

matching airflow velocity and momentum, respectfully, to those

appropriate to actual combustor operation.

Th- test procedures were similar for any of these tests. The

instrumentation was checked each test day. Jet A flowrate was established

at 133 kg/hr. If appropriate, the swirler air differential pressure and

fuel temperature were set for the test condition. Two Malvern data points

were acquired. The system was then switched to the test fuel by activating

the three-way valve. The lowes_ fuel flowrate (118 kg/hr) was set and the i

airflow and fuel temperature condition re-established. Two Halvern data !

points were acquired; the spray was photographed. The test fuel flowrate

wThase itncre est ascondition ed to thaendsecdaontda anacdquisition third leve . lAts, thwith e compl similetion ar care of thfisor holding I

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sequence, the system was momentarily switched back to the Jet A supply and i

then terminated. Another test fuel was loaded into the batch fuel system

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and the delivery lines purged of prior fuel. This sequence of acquiring

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Jet A data and then test fuel data was followed during all four sets of

testing.

Initial Results -- Weber Number Influence

Some preliminary tests were performed to verify that the nozzles were

acting as expected. A single test was performed using a twenty-point

patternator probe to confirm the hollow-cone spray quality. The probe

spanned the spray diameter in a plane 7.6-cm downstream from the nozzle.

The observed pattern is depicted in Fig. I0 where a clearly hollow cone

behavior is evident.

The results from initial tests to determine a Jet A spray SMI)were

different than expected. Several investigators (Refs. 19 to 2!) have

characterized the sprays from pressure-atomizing nozzles and developed

correlations fcr the dependence of SMD on fuel physical properties, fuel

flowrate and nozzle size. For a given fuel, these studies have shown

SMD - WFm DP-n

where WF = fuel mass flowrate

DP = injector pressure drop

m,n = empirically-derived constants in the range:

0.20 < m < 0.25

0.35 < n < C.43

The U_"_RCdata did not flt this form. An investlgation ensued, which

included a comparative chec_ of current and previous Malvern data for a

standard nozzle and a review of the spray characterization literature.

Valid data were being acquired; sufficient signal strengths were being

received by the photodetectors. The normalized size distribution was monomodal and well fit by the Rosin-Rammler distribution function. The Malvern

data acquired with the standard nozzle duplicated previous reaults.

The literature review was fruitful in revealing the probable cause of

the SMD discrepancy. Data presented by Simmons (Ref. 22) indicated a

change in the dominant atomization mechanism as the flowrate through a

pressure-atomizing nozzle was increased. This change was related to the

nozzle Weber number (We) defined as the ratio of fuel inertia forces to

surface tension forces. An expression for We as a function of the nozzle

geometry, fuel properties and flowrate was derived and a critial Weber

number, We , was identified at a value, We = I. Below We , the SMD data

did not ma_ch the above standard correlation while for WeC> We agreement

was achieved up to the maximum We investigated (We = 5). c

Other investigators have also acknowledged the importance of We on

atomization. In particular, Dickerson and Coultas (Ref. 23) noted changes

in the droplet breakup mechanism near both We = I and We = 10. Their

observation of "bag breakup" near We = I coincided with Simmons change in

atomization behavior. Additionally they noted a change to a "shear

breakup" mechanism at higher We. Therefore, just as Simmons observed that

We = I was a lower bound to the range of applicability of the "standard

17
correlation", a We = I0 might represent an upper bound of application.

Atomization correlations developed for I < We < I0 might not be applicable

for high We cases. Indeed, applying tbe expression for We derived by

Simmons to the investigations which developed the correlation revealed

that they were generally restricted to I < We < I0 (Fig. II). The

investigations conducted by Jasuja at Cranfield (Ref. 21) did slightly

exceed this upper limit. Review of th_se data indicated that the high We

values showed the greatest deviation from the empirical correlation.

Because of the sparceness of these points this phenomenon was probably

overlooked. The range of Weber number covered by the nozzle size-fuel flow

demands of the current program is also shown on the figure. Clearly,

operation at We > I0 was to be experienced. These observations highlighted

the need to recognize the application limits of empirical correlations.

Use of the pressure-atomizing injector "standard correlation" would have

been erroneous.

It is noted that a complete SMD correlation was not necessary for this

program since spray characterization data were acquired for every test

fuel. These data are being analyzed by UTRC to develo F such a correlation;

the rcsults of this effort will be published in the future.

Characterization Results

Tests With All Fuels

Data which characterized the atomization of each fuel injected by a

Hago No. 35 nozzle are listed in Table 9. The fuels are listed in

generally decreasing order of atomization quality. As expected, the

measured atomization levels for fuels with similar physical properties

(e.g., Jet A and JP5 or JP4, JP4-S, JP4-A) were also similar. The dominant

physical property appeared to be surface tension. Tetralin and decalin

possessed the highest surface tension and atomized relatively poorly, while

the JP4 fuels, with the lowest surface tension, atomized the best. An

approximately linear influence of surface tenoion was apparent as indicated

by the data plotted in Fig. 12. Viscosity J not systematically influence

the spray atomization (Fig. 13) for the range of viscosity of these test

fuels. These two influences were consistent with the identification of

Weber number as a critical parameter as this variable was responsive to

fuel surface tension but not fuel viscosity. Additionally, both of these

physical property influences differed from dependences associated with the

standard pressure-atomizer SHD correlation, again indicating a change in

dominant atomization mechanism. The included cone angle did not

significantly vary despite substantial changes in the spray SMD. Hence it

was expected that fuel from all sprays would initally have the same

direction.

Te_t_ Kt_E_e_at_e_ F__u_I T_m_e_at._u_e !:

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The data acquired from tests using a No. 35 Rago nozzle spraying Jet A i

and tetralin fuel at temperatures of 299, 311, 328K are listed in Table i0. I

These tests were scheduled in anticipation of reducing the spray SHD {

because of viscosity decreases at elevated temperatures. That is, the I

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standard correlation for pressure-atomizing injectors indicated a

significant dependence of SMD on fuel viscosity. Hence, it was originally

expected that a viscosity reduction would cause an SMD reduction; control

of fuel temperature (and thus fuel viscosity_ was a proposed technique to

control spray SHD. The initial test results nd the complete characterization of all fuels showed that this approach was not applicable. As

demonstrated above, viscosity did not systematically inflaence SMD.

Therefore, despite viscosity decreases of 40 percent for tetralin, the

observed atomization level was insensitive to the fuel temperature. The

mo_e dominant physical property, surface tension, decreased by less than 8

percent over the fuel temperature range invstigated and hence little

measurable influence would be expected.

Tests with Multiple Nozzles

The data acquired from tests with three Hago injectors with nozzle

numbers, NN = 20, 30, 35 are listed in Table 11. Five flowrates were

investigated--the three levels used above plus two lesser flows for the

amallest nozzle to permit acquisition of measurable (i.e., not too small)

SHD data. The expected significant dependence of spray SMD on nozzle size

was documented. The atomization level changed by up to a factor of five

for the range of nozzle numbers investigated. Cone angle variations were

small. Since SHD control by exercising fuel temperature control was not a

viable approach, the atomization goal could be met only by the proper

specification of nozzle size. The SMD data from these tests were analyzed

to quantify the SMD - NN relationship. For the medium fuel flowrate; it

was determined that:

SHD/NN b = constant

with b = 4.0 for Jet A

b = 3.1 for tetralin

The variation in "b" implied that a fuel property influenced the nozzle

scaling. This influence would be in addition to the surface tension effect

observed in tests with the same nozzle (Fig. 12).

HOSt of the atomization levels presented in Table 9 for a NN = 35

nozzle were above the goal of 35 < SMD < 45 _m at a fuel flowrate of 133

kg/hr. Hence a smaller nozzle was often required. Since a value for "b"

was not available for all fuels, the value for tetralin was applied for all

nozzle scaling. Use of b = 3.1 was the conservative approach in selecting

the nozzle. That is, if a fuel would actually be represented by b > 3.1,

then using b = 3.1 would lead to a nozzle atomizing within or below the

goal range. Applying this scaling relationship to the SMD data obtained

with a NN = 35 device led to the specification of the fuel nozzles

indicated in Table 12. Calculated nozzle numbers were transformed to the

nearest available nozzle; four nozzle sizes were to be used. Also shown

are the predicted SMD values; they were within the atomization goal.

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Tests with Swirler Airflow

Data acquired to document the influence of swirler airflow are listed

in Table 13. The NN = 35 nozzle-air swirler combination was mounted on a

25-cm diameter canister which acted as a plenum for the airflow. The two

levels of airflow, represented by the pressure drop across the swirler,

corresponded to matching the airflow velocity or momentum of an operating

combustor. Substantial decreases in SMD were observed indicating a strong

secondary atomization process. Theoretically, it might be argued that the

momentum-matched airflow represented the proper co_bustor simulation. UTRC

experience has not substantiated this belief, however; velocity-matched

airflows have been used with success to screen and select nozzle concepts.

Indeed, data do not exist to clarify this issue. Therefore, while

quantitative conclusions could not be drawn from these data, some reduction

in spray SMD from the data presented in Table 12 was expected.

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SECTION V - TEST FACILITY AND INSTRUMENTATION

The experimental program, including both the combustor calibration and

the fuel-effects and configuration-effects combustion tests, were performed

in the UTRC Jet Burner Test Stand (JBTS). This section of the report

describes the specialized test facility assembled for these efforts. The

instrumentation is detailed, with complete description given for two unique

diagnostics--a transpiration radiometer and Mie-scattered light particle

sizing apparatus.

Test Facility

The experimental program was conducted in the JBTS which is a

self-contained facility with four test cells equipped for high-pressure

combustion tests. The JBTS provides, in addition to the test cells wlth

control rooms, assembly areas, automatic data acquisition systems, and air,

fuel and gaseous nitrogen supply systems.

The test facility consisted of three sections: an air preparation

section, a test and instrumentation section, and an exhaust section (Fig.

14). A specialized fuel delivery system supported the test facility.

The air preparation section provided airflow rates satisfying the

requirements of the test conditions. Air was supplied to the JBTS through

the system depicted in Fig. 15. The multi-staged receiprocating

compressors, capable of pumping a combined flowrate of up to 4.5 kg/s,

provided air at pressures up to 2.7 MPa. The airflow for the combustion

tests was heated by an indirect-oil-fired burner prior to entering the

JBTS; the typical preheat level was 420K. The heated aizflow was regulated

in the test cell and metered by s venturi, with appropriate measurement- of

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

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

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

heated further by use of an electrical resistance-type heater. A plenum at

the heater exit assured that uniform airflow velocity and temperature prGfiles were delivered to the test section; arrays of four the£_nocouples and

four total pressure probes documented this condition.

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The test section housed the combustor liner, providing appropriate

access for a spark ignitor, fuel injector support and other instrumenta- !

tion. This section was fabricated from commercially-available pipe with an

inside diameter of 15.2 cm. The 1.3-cm annular gap between the liner and !

housing permitted adequate backside convective cooling of the burner

louvers. The combustor was supported by links on the dome with an aft

sliding-seal to allow axial and radial growth. The position of the i

combustor in the housing and the layout of instrumentation on the liner and I:

at the combustor exit are described below.

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The exhaust section consisted of a water-cooled T-sectlon and a

backpressure valve. The T-section provide _ a 7.6-cm diameter viewport to !

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permit direct observation of the combustor exit plane via closed-circuit,

color television system. A remotely-operated butterfly valve was used to

control the test section pressure. A high-pressure water quench reduced

the gas temperature upstrea_ of the valve to less than 7O0K to prevent

damage to it.

The fuel delivery system consisted of three subsystems: a startup fuel

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

supplied to the test ce)l from underground storage tanks by positive

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 acquired for the

combustor operating on Jet A-U prior to operation on any test fuel. Jet

A-U had properties identical to the Jet A test fuel; the drummed test fuel

had been extracted from this source early in the program. The underground

Jet A tank was isolated for this program; no additions were made to this

tank once testing commenced. Drum quantities of the test fuel could be

delivered by the test fuel subsystem which was capable of delivering 4.6

liter/min 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 system and normally-closed valve in the test fuel system

were switched in unison to provide a rapid, positive change in fuel. A

Model C-12 Micromotion mass flowmeter was located in the common fuel

delivery line _t the test rig. This meter sensed the coriolis forces

induced by fuel flowing through a curved tube to determine the mass flow.

The meter contained no moving compcnents (e.g., turbine vanes) and hence

the rate measurement was independent of the viscosity. The nitrogen

subsystem was available to purge the fuel nozzle and delivery lines inside

the combustor rig and to cool these items during the setup of the test

condition. The fuel system is depicted as part of Fig. 16.

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Instrumentation

The test facility was instrumented as described below. The parameter_

measured are listed in Table 14 and schematically indicated in Fig. 16.

Measurements were made to document the airflow rate, pressure and

temperature approaching the model combustor. The airflow rate was determined using a venturl with a 2.286-cm throat diameter; pressure and

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

distribution of temperature and total pressure at the test section inlet !

were documented using arrays of four thermocouples and four total pressure i

probes. The test section housing containcd four static pressure taps to i

document both the axial static pressure gradient in the airflow external to i

the burner and the p_essure at the combustor exit_

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The fuel supply contained provisions for acquiring pressure and I"

temperature measurements necessary to control the flow. A thermocouple was j

inserted through the fuel tube to the nozzle vicinity to document the [

temperature of the injected fuel. As described above, a Micromotion mass I

flovmeter was used to determine the fuel flowrate. A dc voltage source, I

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interlocked with the fuel switchover valves, produced a signal for the data

system to identify data points acquired when operating with the test fuel.

The model combustor was instrumented with thermocoup!es to document

changes in the combustor metal temperatures. Three bundles of 13 type K

thermocouples were mounted on the combustor liner--two thermocouples

mounted on each louver and one on the dome for each bundle. The layout of

these sensors formed axial arrays between alternative rows of the louver

combustion air holes. The photograph of the combustor liner (Fig. 3)

illustrates the liner thermocouple layout. The location of the

thermocouples coincided with the end and 2.5 cm downstream of the inner

louver lip.

Two types of radiometers were used to document the radiative heat

loads--transpiration and thermopile devices. The thermopile unit was

representative of a conventional approach to radiation measurement. Such a

device requires a window to isolate the sensor from the combusting medium

and thereby eliminate convective heat transfer. Windows are difficult to

use adjacent to a sooting environment. Deposition on the surface can alter

the transmission and hence the level of radiation sensed. A solution to

this problem is to recess the window, but this practice narrows the view

angle, prohibiting acquisition of full hemispherical fluxes. As explained

below, a transpiration radiometer does not use a window and permits

placement of the sensor at the combustor wall.

Two transpiration-type radiometers were mounted on the dome of the

burner. Each radiometer was a prcbe-like device constructed from three

concentric tubes; it had 1.6-cm OD and was approximately 25 cm long (Fig.

17a). The outer two tubes provided a delivery-return cooling loop to

ensure survival of the probe, while the central tube ducted a metered flow

of gaseous nitrogen to the probe tip. The tip was covered by a tightlywoven steel screen which permitted the nitrogen to seep out of the probe

(Fig, 17b). It was mounted to place the screen flush with the combustor

liner to acquire the full-hemispherical radiative flux.

The screen was the radiative load sensor. It was heated because of

heat transfer from the combusting medium and cooled by the convective flow

of nitrogen. At steady-state, the energy removed by the nitrogen must

equal the input energy. Direct measurement of the energy gain of the

nitrogen wns not possible since it would have required measurment of the

nitrogen temperature leaving the screen. However, if the screen was a

perfect heat exchanger, the screen temperature would equal the exit gas

temperature and therefore (ideally):

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Ideal Energy = WN2 * CPN2 * (TSCREEN - TN2UP)

where WN2 = nitrogen mass flow L

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CPN2 = specific heat of nitrogen [

TSCREEN = temperature of probe screen I

TN2UP = temperature of nitrogen upstream of screen _

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As shown by Moffat (Ref. 24), with sufficient nitrogen flow, the gas

boundary layer will be blown-off the tip and only radiative transfer would

heat the screen. The occurrence of blowoff depends on the flow of the

inner, combustin E flow; experiments with a flat plate suggest that the mass

flux must exceed 8 percent of free stream value to achieve this condition.

During this mode of operation, as the nitrogen flowrate is reduced, the

probe temperature rise (screen minus upstream nitrogen temperatures) would

increase while the energy input remains constant. Only at low nitrogen

flow would the hot gas boundary layer re-attach, a situation to be avoided

because the input energy would have destroyed the screen. Data were

acquired at various nitrogen flowrates during combustor shakedown tests to

confirm measurement of radiative hear transfer only (Fig. 18). As expected,

the probe temperature rise did vary but the input energy remained constant.

During combustor testing, a nitrogen mass flux of approximately 6 gm/s/cm

was used to assure operation in this mode. All probes were calibrated by

the Pratt & Whitney Aircraft Commercial Engineering Heat-Transfer Laboratory at elevated pressures to account for the non-ideal heat exchanger

behavior of the tip screen.

Three, water-cooled thermopile radiometers were acquired from

Medtherm, Inc. to document the changing pattern of zadiative heat transfer

within the combustor. These devices were mounted on the test section

housing to view the combusting medium through the 1.2-cm diameter

combustion air holes located in louvers I, 2, and 3. The radiometers were

designed to have a narrow view-angle (effectively, 33.43 deg; form factor =

0.0215) to allow locating them on the case to view the ¢ombusting gas but

not the metal liner. Since these devices accepted radiation over a

relatively narrow angle, the indicated radiative load could be either

higher or lower _han the hemispherically-averaged level measured on the

dome. However, the three case-mounted devices did provide an indication of

the axial distribution of radiative heat transfer and how this distribution

was influenced by fuel chemical properties or test condition. These radio- i

meters used a thermopile sensor located behind a sapphire window. The

narrow view angle derived from a significantly recessed window which, in

turn, was continuously purged by nitrogen. The repeatability of Jet A-U

data indicated that no window fouling occurred. Furthermore, the devices

were re-calibrated by Medtherm after completion of the fuel-effects tests

and found to deviate from the original calibration by loss than 2 percent.

The combustor exhaust products were probed to determine the

temperature distribution, average gaseous emission levels, smoke emission

level, and particulate size and number density. The measurements utilized

a serial buildup of intrumentation sections as depicted in Fig. 14. The i

combustor exit temperature distribution was determined by using six thermocouple rakes containing a total of 22 sensors. The thermoccuples were Type I

B (PT61_/PT30RH) devices concentrically mounted in a vented radiation !

shield. The exposed portion of the thermocouple sheath and the radiation t

shield were fabricated from a platinum al_oy thereby allowing a thermo- 1

couple maximum use temperture of approximately 1850K. The average gaseous l

exhaust emissions were determined from examples extracted by four ganged i

sampling rakes containing a total of 20 sampling orifices. The samples !

were analyzed to determine unburned hydrocarbons, carbon monoxide, carbon

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dioxide, oxygen, and total nitric oxides. Table 15 presents the types and

ranges of the exhaust gas analyzers. Smoke emission levels were determined from samples extracted by three, ganged, steam-cooled probes. The

probe orifice diameter (1.55 mm) was sized to achieve isokinetic sampling;

the sampling procedures were those specified by SAE ARP 1179. The layout

of these several combustor exit plane probes is shown in Fig. 19. The flow

blockage was no_ as great as the figure might imply; the array did not

measurably backpressure the combustor.

Particle size and number density were determined at the combustor exit

from an in-situ, spatially precise technique--namely, from the scattered

light emanating from an approximately 15 mm sample volume on the combustor

centerline. This non-intrusive approach was adopted because of the belief

that probe sampling would alter the character of the soot; particulate

agglomeration would be likely.

The scatered-light signals were interpreted according to Mie therory

of light scattering. This technique has been detailed previously by

several authors (Refs. 25, 26, 27) with a critical assessment of the

accuracy of it given by Bonczyk (Ref. 28). In brief, this theory predicts

the intensity of light scattered by particulates as a function of the

scattering particle properties, the scattering geometry and the incident

intensity:

I = K * I0 * N * PHI

wh_re I = Light intensity scattered by particles

_I incident light intensity = complex scattering function

K = constant includit,g the scattering solid angle and the

optical sample volume

N = particulate number density

The scattering function, PHI, is dependent upon the size parameter, x, the

scattering angle, e, and complex refractive index, n:

PHI = PHI (x, e, n)

where x = _D/I, % = the wavelength of the scattered light

D = the particle diameter

PHI is also responsive to the polarization of the light. Strictly, this

description is accurate only for spherical particles of uniform size.

Extensions of the theory to permit definition of polydispersions result in

greater analytical and experimental complexity. For combustion

applications, where the particulate shape is non-spherical, it is difficult

to determine all the parameters of the polydJspersion. Therefore, for such

appliations, it is common to assume a monodisperse particulate size

distribution. This approximation (and the accompanying assumption of

spherical particles) limits the accuracy of the D and N determinations.

25
The evaluation of particulate size and number density relled upon the

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

a zixed polarizatlon ot the llght (chosen to be perpendicular to the

scattering plane), the ratio of llght intensity at two different angles, +!

ana 62 is:

l(Gl)/l(e2) = PHI (D,e1,n)/PHI(D,02,n)

Thls ratlo is a function of D alone for given values of the complex

retractlve xnoex and scattering angles. In this program, values ot el = 4>

deg and @2 = 13D de_ were used; the scattered llght had a wavelengtn of

514.5 rim. The dependence of the ratio of scattered llght on D is depicted

in Fig. 20 for two values of n. Note that the theory permlts size determinatlon for D < 0.3 _m; for larger diameters, the ratio is multlvalued and

are unambiguous size determinatlon cannot be made. The proper value for

the complex inaex of retractlon of the combustor exhaust particles was not

known; the value llkely depended on the chemlcal compositlon of the particulates. The two values used to generate the curves in Fig. 20 were

obtalned from measurements elther on graphlte or on soot from an acetylene

flame. For the valld range of diameter determlnation, the uncertalnty •

introduced by tOese two n values was not great, however; toe value for

graphlte (n = 1.94 - 0.66i) was used in toe data reduction. Once D had

been determined, the particulate number density, N, was calculated from the

scattered llght intensity meaured at 61 and the known geometry of the

scattering setup.

The particle slzing apparatus assembled for this program is shown in

Fig. 21. The incident llght was produced by an argon-ion laser wlth an

output power level of approximately lw at a wavelength of 514.5 nm. The

polarizatlon ot the output beam was rotated to be perpendicular to toe

scattering-plane; the beam was chopped at a frequevcy of 2008 Hz. The beam

was oirected through a recessed sapphlre wlndow, across the combustor

exhaust, tOrough a second wlndow and on to a laser powermeter. Two

scattered Ixght detector assembhes were rigidly attached to the test duct,

one at 45 deg and one at 13) deg from forward scattering. The fabrication

tolerances ot the assembly mountings were specified to assure precise

allgnment ot them; during installation of lois apparatus it was observed

tnat tne beamF from two He-Ne allgnment lasers intersected on the test duct

centerltne. Each detector assembly contaxned a sapphire wxndow, a

polarizing disk, a narrow-pass f11ter (centered at 514.5 rim) and a fast

llnear focused (EMI type 980/B) photomultipher tube (PMT). The solld

angle of the scattered hght was defxned by two 3.1 mm dia appertures

(separated by a distance of 20.0 cm) located along the detector centerlxne.

The output trom each PMT was input to a lock-in amplxtier whxch was

referenced to toe chopper frequency. Thxs setup enhanced the signal-tonoxse ratlo by provxding an output voltage proportional to the difference

between tne laser-stxmulated scattered Ixght and any random hght which

might have been detected. !

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The laser beam path also contained two focusing lenses. Initially i

these lenses were not in the optical path. During combustor sOakedown

tests, the quallty of the laser beam exiting the test duct was observed by !

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use of a television system. No significant beam steering was observed;

however, substantial beam diameter growth was observed. That is, the

" 1.3-mm diameter laser beam had grown to fill the 12-mm diameter exit port.

This growth was attributed to "thermal blooming" which occurs as light

passes through gases which possess large temperatare gradients. The

thermal gradients produce gradients in the index of refraction which

result in a lens-like expansion of the ray. It was suspected that the

blooming occurred in the window recesses where cool nitrogen purge flow and

hot combustion products were unavoidably mixed. The lenses were installed

to focus the laser beam on the test duct centez!ine to minimize this

problem. Once the lenses were added, the beam quality exiting the test

duct substantially improved. The exit beam diameter was reduced to less

than 2 mm; geometric considerations of the focusing implied that a 0.5-mm

diameter beam passed through the measurement volume. An alternative

solution, use of heated purge flow, was not compatible with the window seal

design.

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SECTION "I - COMBUSTOR TEST CONDITIONS,

PROCEDURES, DATA ACQUISITION AND REDUCTION

The principl_ variable investigated in this program was fuel chemical

properties. Only a single airflow condition was used, with fuel injectcd

at three flowrates for each test fuel. The matrix also included test

replications to permit dete_£_nakion of the statistical c, ,sistency of the

data. This section of tilerer_;t details th_ test condzt ns and

procedures, and specifies tLe _anner in which the data were acquired and

statistically analyzed.

Test Conditions and Procedures

The singl airflow condition used in this program simulated high-power

operation of a gas turbine engine. Each fuel was tested at the three flowrates required to produce ideal combustor exhaust temperatures or 1247K,

1346K or 1473K. These three temperatures were the ideal temperature levels

associated with combusting Jet A at fuel-air ratios of 0.015, 0.018 and

0.D22, respectively. The actual flowrates for each fuel were determined

from thermochemical c_Iculations using the chemical properties determines

from the fuel analyses. The combination of airflow parameters and

combu[tor exit temperatures defined three test conditions indicated in

Table 16.

These conditions were established in both of two phases of tests:

fuel-offects tests and configuration-effects tests. In the fuel-effects

phase, all twer_y-five test fuels were evaluated in a single burner

c,_nfiguration. In the configuration-effects phase, three test fuels were

evaluated in two modifications to the above baseline burner. These two

configurations, described in Sect_o_t III, provided either a higher or lower

primary zone equivalence ratio than that of the baseline.

The test procedures were identical for all tests in both phases. The

data a=quisition system was set up each test day. Pressure transductr and

thermocouple references were checked; flowmeter, analyzer and radiometer

outputs were _eroed; signal amplifiers were calibrated. A druu of the test

fuel was installed with approximately 12 liters pumped through the _elivEry

and return lines to purge them of previously-used fuel. The appropriate

JBTS support sysCems were activated; pl,r_e flows were established through

the sample probes, radiometers and f'_el delivery line. Combustor airflow

was initiated and heated by both the indirect-fired and electrical heaters.

The fuel purge _-as termina=ed and Jet A-U introduced. Because of the high

inlet air temperature, _.he fuel ignited spontaneously at a minimal flow,

avoiding a sudden increase in burner pressure. The fuel flowrate was

increased and the airflow parameters (pressure, temperature, flowrate) i

adjusted to the Condition i setpoints. Probe purge flows were terminated I

and steady-state conditions verified by obse,_vation of the exhaust gas I

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temperature and species concentrations. {

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Data were acquired for operation on Jet A-U prior to combusting I

test fuel. If the test fuel was the first to be investigated un the test i

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day (multiple fuels wele evaluated in a day), data were acquired at all

three conditions. For subsequent fuels in the test day, data were acquired

only at Conditicn i. For each condition, three data points were recorded

on the data acquisition system and three smoke samples acquired. Key parameters displayed in the control room were hand-recorded to provide a reference of ourner behavior. These readings were frequently reviewed during

Jet A-U tests prior to test fuel operation to confirm that the combustor

was firing in an expected and repeatable manner.

After obtaining data for Jet A-U fuel, the fuel Gupply wa switched to

operation on the test fuel previously loaded in the system. Switchover was

always accomplished at nominal Condition ! setpoints; the simultaneous

activation of solenoid valves provided an uninterrupted flow of fuel and

the burner never extinguished. Condition I operation was established for

the test fuel and three data points and smoke samples acquired. The fuel

flow was increased and airflow parameters adjusted to achieve ConditJo;, 2

and Condition 3 in sequence, with three data points and smoke samples

acquired at each. Upon completion of this three condition sequence, the

fuel flow was decreased and burner parameters adjusted to re-establish

Condition I. Similar data were acquired for this condition and

subsequently again for Conditions P and 3. This sequence was repeated a

third time to provide a total of nine data points for each test condition.

These data were statistically analyzed as described below to determine

whether consistent, repeatable data were being acquired.

After completion of these sequence tests, the fuel system was switched

to the Jet A-U supply and then flow was terminated. Purge gas was

established through the sampling probes prior to this process to avoid

ingestion of unburned fuel; the fuel lines were purged immediately upon

fuel termination. All systems were secured if the tests planned for the

day were completed. Otherwise, the test fuel was changed, fuel lines

purged and the Jet A-U/test fuel sequence described above was executed

again.

Data Acquisition and Reduction

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

data acquisition system which stored the information on magnetic tape for

subsequent computer processing. The data system accepted data on up to 25

channels, 10 provided with signal conditioners, and the remainder comJ

patible with preconditioned input signals. The system was capable of

controlling and accepting data from submultiplexers such as pressure and i

'_ thermocouple scanning switches. The data channels were scanned sequen-

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tially at a rate of 12 channels per second and whenever a submultiplexer

was connectad to a channel, all ports were sampled before proceeding to the !

, next channel. An analog-to-digital converter digitized the data and an i

incremental magnetic tape recorder stored it for subsequent computer 17

processing. The format of the tape was structured for compatibility with j

the UTRC UNIVAC 1110 digital computer. I

Data reduction was c_mple:ed in the following three steps: Ii

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I. Data tape point-by-point reduction

2. Normalization to standard test conditions

3. Precision assessment

Data Tape Reduction

The data system magnetic tape was reduced by use of an existing

computer progrr_. This code applies the appropriate calibration factors to

each signal to provide engineering units for pressures and temperatures for

calculation of parameters of interest. Among those selected for this

program were: airflow rate, fuel mass flowrate, combustor reference

velocity, radiative heat flux, exhaust emission indices, fuel-air ratio

from either metered flows or exhaust species, particulate size and number

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

primary zone equivalence ratio, ideal combustion temperatures for either

the primary zone or overall combustor, and combustion efficiency. Averages

of pressures and temperatures which characterized the inlet airflow or

combustor exhaust were also calculated. The output from this 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., open thermocouples) with 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.

Test Condition Normalization

In any test program, attaining the precise values of the test

condition parameters is difficult. The conditions achieved in this program

generally matched the desired parameters to within 0.5 percent. In an

attempt to minimize the influence of even these small deviations, relationships were derived to normalize the performance parameters to the exact

test conditions. These relationships were either analytical expressions,

correlations or complex relationships expressed by analytical models (e.g.,

influence of pressure on ideal combustlon temperature). A listing of the

test parameters and the calculated and measured performance parameters is

given in Table 17. The parameters designated by the asterisk under the

Parameter Type column were those which established the test conditions

and were set according to the values specified by the test matrix. The

parameters whicl were not test parameters were designated either as

measured paremeters or calculated parameters. Measured parameters included

those that were directly measured or those which required only a straightforward arithmetical manipulation (such as obtaining the averages of four

combustor entrance air temperatures to obtain the average entrance

temperature). Calculated parameters were those which were derived from the

measurements and in general were dependent on more than one test parametezo

The methods for normalizing the parameters to the standard test values

and an indication of which parameters were subjected to a precision analysis are also indicated in Table 17. In the case of the test parameters

themselves, the normalized value was that specified in the test matrix.

Most measured _arameters were normalized by use of influence coefficients

(IC). An influence coefficient is a weighting factor which specifies the

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percentage change in the measured parmmeter for a 1 percent change in an

independent (test) parameter. This approach is equivalent to correcting

the parameter by mathematically forming a first-order expansion about the

measured value (i.e., a single term Taylor series) and hence was an

adequate technique for small departures from the desired test conditions.

The influence coefficients were obtained either from derivatives of simple

equations relating measured and test parameters (e.g., fuel pressure-fuel

flowrate dependence) or from the response of computer model calculations

from perturbations of the test conditions (e.g., influence of pressure on

the combustion temperature). In particular, the radiation measurements

were normalized by the quotient of ideal radiative loads predicted for the

desired and actual test conditions. In these calculations, the emissivity

was computed from the model of Lefebvre (Ref. 29). An existing computer

code tc _tedict liner temperatures was used to develop their IC from

results obtained from parametric perturbations of the test parameters

(airflow, fuel flow, etc.) The trace exhaust emission species (UHC, CO,

NOx) were normalized by use of correlations developed by Sarli (Ref. 30).

Calculated parameters were normalized by performing the calculation with

the normalized parameter values.

Precision Asssessment

For each of the performance parameters subjected to a precision

analysis (see Table 17), the following statistical properties were

calcu!ated:

1. The mean value

2. The standard error of estimate

3. The interval about the mean within which the true means lies

to a confidence level of 90 percent

4. The interval about the standard error estimate within which

the standard deviation lies to a confidence level of 90 percent.

Precision is a measure of the repeatability of data• It is customary

to express precision £n a quantitative manner by using the standard error

of estimate. This statistic is often erroneously referred to as the

standard deviation. However, the standard deviation is a measure of

precision for an infinite set of data while the standard error of estimate

is a measure of precision for a set of S (finite) data. In practice, for

reasonable values of S, the two statistics have essentially equal values •

The use of properties of the standard error curve to describe the precision !

of a set of S data is based upon the assumption that the data are randomly i

distributed about the mean of the data. It can be shown that for !

reasonable values of S (> 30), this assumption is valid. However, for t

small values of S, there is a non-zero probability that the data are _ot

randomly distributed about the mean value so that the calculated standard i

error of estimate will differ from the true standard deviation value. I!

I

In this program nine values were obtained for each parameter at each . !

i

test condition. Therefore, there was a reasonable probability that each set

of data was not randomly distributed about its mean value and the mean {

value differed from the true mean (assuming that the data were otherwise I

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31 [

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free of bias). To assure that the statistics describing the precision of

the data were reliable, it was necessary to use statistical techniques

applicable to small data sets. No inference procedure was capable of

producing an exact result. Instead, a statistic was calcualted that had a

specific probability of being correct. One technique applicable to the

present case is Student's t-test. This procedure assumes the standard

deviation calculated for a small set is reliable (i.e., the data _re

randomly distributed about the mean value of the set) and estimates the

degree to which the true mean for the data differs from the calculated

mean. The determination of the confidence interval for the mean value

requires that the confidence interval for the standard deviation be

specified. It also is not precisely known for small sample sizes, and

therefore, a "Chi-square" method was applied to establish the confidence

interval for the standard deviation.

A computer program was written which accessed all data contained in

Summary Tables and grouped the points common to a test condition for each

fuel. These groups were normalized and analyzed for precision. A

publication-quality printout was produced and bound to represent one part

of the Comprehensive Data Repoct for this program.

.J

32

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SECTION VII - COMBUSTORTEST RESULTS: FUEL-EFFECTS

_he principle objective of the program was to quantify the influence

of fuel chemical properties on gas turbine combustor operation, emissions

and heat load. As described in previous sections of this report, fuel

physical properties were de-emphasized by achieving highly-atomzzed, and

hence rapidly-vaporizing, fuel sprays. Test fuels were specified to

present vide ranges of fuel hydrogen, total aromatic and naphthalene

contents. This section of the report presents and discusses the data

acquired from combustion tests with these fuels to determine the chemical

property influences on the burner.

General Combustor Operation and Data Quality

The baseline combustor configuration, which was used in all of the

fuel-effects tests, operated in a consistent manner. The combustion efficiency (determined from exhaust gas analyses) was always 99.9 pct or

greater. Often the unburned hydrocarbons and carbon monoxide were below

the threshold detection level of the analyzers. The NOx emissions were

relatively constant at a level EINOX ffi12 to 14. The combustor exit

temperature pattern factor was typically 0.12 +_0.01 at Test Condition I,

increasing slightly to 0.14 + 0.02 at Test Condition 3. On the last test

day, the indicated pattern factor for conditions 2 and 3 rose to 0.18 +

0.02. One fuel tested this day was Jet A which had been tested several

other days as the startup fuel, Jet A-U. All other Jet A data (radiation

load, emissions, liner temperatures) were in agreement with values

previously obtained with Jet A-U. Hence, it was concluded that these

higher pattern factors were anomalous; inspection of the exit thermocouple

rakes indicated that, because of coolant leaks, some temperature

measurements were affected. Since the Jet A-U radiation load, liner temperature and emission data were similar to the levels obtained in previous

tests, the associated test fuel data were considered valid and included in

the analyses. These constant and relatively low levels of pattern factor

indicated that all fuels were injected and distributed similarly. While

gross mixing patterns in the combustor would tend to smooth variations in

fuel concentration, experiences with other burners would indicate that the

low pattern factor values would not be achieved if significant maldistribu- ,

tions were present. ,,

The combustion test data were acquired from a repetitive test cycle as !

described in Section Vl. Each test condition was established three times,

with three data points obtained for each setup to develop a set of nlue !

data points available for statistical analysis. A high degree of test con- '.

dition repeatability was achieved That is, the standard error for the

nine data point set was typically less than 0.8 pct of the mean value of I

inlet air pressure and temperature, air flow and fuel flow. Furthermore, i

the conditions achieved very nearly matched the desired conditions, I

assuring that the data normalization process would impose mmall changes to i

the measured data. Typically, the actual conditions deviated from the !

target values by less than 0.9 pct. As a result of the care exercised in

g

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repeating test conditions, the combustor performance parameters were also

very consistent, with the following typical values of data set standard

error: radiation heat transfer, 2 pct; liner temperature, 0.3 pct; smoke

number, 1.5 units; exhaust particle size, 5 pct; and particle number

density, 25 pet.

The fuel effects data were acquired from tests performed on several

test days with multiple fuels evaluated each day. The day-to-day variation

and the variation during a test day of the combustor operation were small.

Figure 22 presents the dome radiation data acquired from combusting Jet

A-U fuel each test day prior to each test fuel. The abscissa has been

scaled to reflect th= relative atomization of the fuel according to the SMD

- NN- (b = 4.0) relationship developed in Section IV. During each test day

(each day is represented by a different symbol), the variation in the data

was within 2 pct of the mean value. In general a day-to-day comparison

cannot be made since differing levels of atomization would be expected; as

indicated on the figure, over the range of nozzles used, more than a

three-fold increase in the SMD for Jet A-U was predicted. Since an SMD =

60 _m was measured for the fuel flowrate associated with Test Condition 1

and NN = 35 (Table 9), the SMD predicted for NN = 40 was 100 _m. This

droplet size was substantially larger than the calculated critical diameter

required to avoid fuel physical property influences. The rather slight

change in radiation leve) suggests that such large changes in SMD did not

occur. This could be true if airflow-induced secondary atomization

processes existed which resulted in high levels of atomization always being

achieved. Data were acquired for operation with the same nozzle (NN = 32)

on three test days. The daily mean values were within 5 pct of the mean

for all data with this nozzle.

Three case-mounted, narrow-angle radiometers were used to sense

changes in the axial distribution of the combusting gas radiation. One

device was aligned with a large combustion air hole in each of louvers I, i

2, and 3 (hence referred to as a liner radiation measuremerts). It is

important to note that these devices did not measure the total radiation to

the liner at the measurement point. The narrow view-angle (33.4 deg

included effective angle) limited the accepted radiation to only 2.2 pct of

the potential hemispherical solid angle source. Hence, assuming that the

radiative heat transfer was uniform over this view angle, the liner

radiation data were e_pressed as a liner radiance (radiation flux density

per solid angle, kW/m_/sr). Figure 23 presents data typically obtained for

all test fuels. As indicated, the radiance increased in witching from Jet

A-U to ERBS and the radiance distribution shifted with changes in test !

condition. The former behavior was expected because of the generally i

poorer fuel chemic_l properties of ERBS--Iower hydrogen, higher total

aromatics and naphthalene contents. The shift in radiance distribution i

resulted from changing local fuel-air ratios as fuel flow was increased.

Table 18 presents a calculated equivalence ratio in the vicinity of each of }

the first three louvers. These values are based upon the airflow i

distribution determined from the combustor calibration activity assuming I

that the stoichiometry is established by airflow from the upstream louver; i

the air entering a combustion air hole was assumed to deflect downstream !

and thus not dilute the mixture at that port. For Condition I, the l

i

34 1i

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stoichiometry in the vicinity of louvers 2 and 3 was very fuel-lean

providing a rather non-luminous flow, while at louver 1 the equivalence

ratio was transitioning from the fuel-rich primary to a fuel-lean

condition. Hence, high radiance levels would be expected at louver I with

low levels for louvers 2 and 3. For Conditions 2 and 3, the extent of the

fuel-rich region and its average equivalence ratio grew; an increase in the

quantity of soot produced in the primary zone would be expected. The high

radiance levels measured at in louvers 2 and 3 indicate the presence of

carbon in these regions despite a local flow characterized by overall

fuel-lean stoichiometries. Apparently the higher levels of soot produced

in the richer primary zones persisted further in these regions before being

completely oxidized.

The liner radiance levels obtained for all test fuels are compared in

Figs. 24 and 25 for Test Conditions I and 3, respectively. The second

ordinate represents the equivalent, uniform full-hemispherical, radiation

flux required to produce the associated liner radiance. These values are

not the true liner radiation load since significant spatial vaziation of

the radiation source would be expected. Clear trends in the radiance

levels are evident. Importantly, these data confirm that the combusting

flow structure was not significantly altered by any of the test fuels.

That is, for Condition I (Fig. 24) the radiance in louver 1 was always

greater than in louvers 2 and 3. Furthermore, the variation imposed by

changing chemical properties was small compared to the difference between

louver 1 and louvers 2 and 3. Similar distinctive trends were evident for

Test Condition 3 (Fig. 25). Such trends could not be easily identified for

Test Condition 2 since the radiance levels were nearly constant (as

indicated in Fig. 23). However, it was plausible to conclude that since

the flow structares were not significantly affected by fuel properties for

Conditions 1 and 3 they also would not be affected for Test Condition 2.

This independence also affirmed that for each condition, every fuel was

similarly atomized and distributed within the burner.

Chemical Property Influences

The influences of fuel chemical properties on the combustor behavior

were reflected by the dome radiation, liner temperature rise, exhaust smoke

number, and particle size and number density data. All of these data indicated that tho principle result of variation of the chemical properties was

to alter the quantity of soot formed in the front end of the combustor. ,

That is, fuels with a high indicated propensity to soot (i.e., lower smoke

point) produced high radiation heat loads and exhaust soot concentrations, !

with correspondingly high levels of liner temperture rise and smoke number, t

respectively . Data a_alysis indicated that the chemical property

influences on each of these operational parameters were similar. Further,

the influences determined at one test condition were similar to those I

determined at the other two conditions. Therefore the following detailed I

discussions of data will focus on one parameter, dome radiation, as docu- Ii

mented at Test Condition 2; the general results for all three parameters at

all conditions are presented in a summary at the end of this section. i

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35

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Soot Formation in Combustors

Soot formation processes harp been studied by many researchers;

several, comprehensive reviews of these efforts exist in the literature

(e.g., Refs. 31-33). All of these affirm that the detailed chemistry of

soot formation is not fully established. The general trends of sooting

propensity were established nearly three decades ago. For premixed

flames the increasing tendency to soot is (Ref. 34):

acetylenes < olefins < paraffins < benzenes < naphthalenes

while for diffusion flames the trend is (Ref. 35):

paraffins < olefins < acetylenes < benzenes < naphthalenes

It has been argued (Refo 36) that these sequences do not reflect the true

influences of hydrocarbon structure alone, but rather are dictated by a

temperature-sensitive controlling mechanism. That isj the soot produced by

a flame is a result of two competing mechanisms--formation of soot precursors during fuel pyrolysis and oxidation of the precursors in the Flame.

For prmnixed flames, both mechanisms exist, with the oxidation mechanism

increasing more rapidly than the formation mechanism as the temperature

increases. Hence soot production decreases with increasing temperature.

The order of increasing sooting tendency indicated above for premixed

systems corresponds to decreasing flame temperature, or equivalently, decreasing oxidation. In contrast, for diffusion flames, soot is formed in

the fuel-rich regions where the oxidation mechanism does not exist. Increasing temperatures enhance the pyrolysis rates and result in higher soot

levels. The above sequence for diffusion flames follows a higher flame

temperature--higher sooting tendency trend. While this separation of

controlling mechanisms may be correct (and hence the true influence of

hydrocarbon structure not represented by the above sequences), for systems

in which fla_.e temperature is not controlled, the sooting tendency of

these hydrocarbon groups would correspond to the above trends.

Detailed studies of soot formation indicate that for the many types of

hydrocarbon molecules contained in avaition fuels, two principle soot

formation mechanisms are active [Fig. 26 (Ref. 37)]° For aliphatic hydrocarbons (i.e., paraffins, olefins, acetylenes) oxidative and thermal

pyrolysis of the parent molecule leads to acetylenic-type compounds. It

has been suggested (Ref. 36) that these species undergo radical reactions

to form conjugated structures, stabilized by chemical resonance, which can

survive the high temperature regions of a flame. Such precursors subsequently proceed through nucleation and growth stages leading to soot particles. For aromatic hydrocarbons, fragmentations can occur at high

temperatures (above 1600-1800K) leading to precursor formation and reaction

as above. At lower temperatures, parent aromatic molecules can be pyrolyzed to radicals which undergo condensation reactions. The resulting polynuclear, cyclic structures would be favorable nucleation sites, with subsequent growth to soot particles. Multi-ring aromatic molecules could also

follow these paths, either fragmenting to provide soot precursors or

pyrolyzing to lead to nucleation sites. For multi-ring structures, it

36

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would be expected that the nucleation sites would be larger than tho_e from

benzene-type molecules, representing an advanced step in the growth

process. In diffusion flames, where the fuel heating rate is slower than

the chemical reaction rates, pyrolysis would precede fragmentation and

hence the sooting tendency of aromatics would favor the condensation route.

This is considered to be the dominant route in the combustion tests

performed in this program.

Data Analysis Methodology

The data acquired in this program were analyzed to determine the influence of fuel chemical properties on the combustor, with the resulting

trends compared to those indicated by the sooting tendencies and

mechanisms presented _bo_e. The chemical property influences were discerned from analysis of two sets of data--data from limited tests which

provided parametric variations in fuel properties, and data from all tests

to include the widest range of chemical properties.

Tests were performed with fuels offering parametric varlation of

chemical properties in an attempt to isolate the influence of hydrogen,

total aromatics and naphthalene content. It is appropriate to recognize

which chemical constituents were actually varied as indicated by the

details of the fuel analyses (Table 5). The hydrogen content variation, at

constant total aromatics and naphthalenes, was principly achieved by

substitution of cyclo-paraffinic hydrocarbons for normal-paraffins. The

total aromatic content variation, at constant hydrogen and naphthalene

content, was achieved by substitution of various paraffinic hydrocarbons

for benzene-type molecules° The mix of paraffinic hydrocarbons in the fuel

with lower total aromatic content was also shifted toward multi-cycle

saturates in an effort to retain a constant hydrogen content. The

naphthalene content variation, at constant hydrogen and total aromatics,

resulted from exchange of benzene- and naphthalene-type molecules.

The data acquired from tests with all fuels were analyzed to discern

chemical property dependence of the combustor parameters for the wide

ranges of chemical properties offered by the twenty-five fuels.

Multi-variable regression analyses were performed. The limit_ of this

approach were recognized. That is, in performing regression analyses, one

attempts to determine the best f_mctional relationship between the

dependent variables (combustor performance parameters such as dome

radiation, smoke number, etc.) and the independent variables (fuel

properties such as hydrogen content, smoke point, etc_). Often several

relationships are formulated and evaluated. Unfortunately, since

regression analyses do not derive from first-principle considerations, no

general guide is available for their formulation, and poor representations

of the data can result solely from assuming improper functions. The !

quality of the data representation by a _unction was evaluated by using the

square of the correlation coefficient, R-. This term indicates the

fraction of_the total variation in the data that is represented by the J

z

function; R 1 would denote a relation which perfectly tracks the

observed data. The functional expressions developed during this effort i

wer_ good-to-excellent representations of _he data with R > 0.7 alw'ys

37

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achieved and values greater than 0.9 often encountered. Hence, reasonable

functional forms were evaluated, especially for cases which achieved R >

0.9. Furthermore, because of these R2 values and the large number of test

fuels, the correlation coefficients were statistically significant, with

distinct correlations obtained to a confidence level exceeding 0.99. The

fuel property regression equation was limited to include exponenti_

functlons of fuel properties such as:

combustor parameter - HCIAC2NC3

where: H, A, N represented the percent hydrogen, total aromatics and naphthalene contents, respectively, and CI, C2, C3 were constants optimized

during the regression process. Several fuels had total aromatic or

naphthalene contents near or equal to zero. The above exponential form

could not be used in regression analyses for fuels with zero concentration

and, for fuels with low concentrations, was susceptible to large error because of the uncertainties in the property analyses. For such instances,

the fuel property was expressed as the difference from total concentration

(e.g., 100-N). Among the several fuel property functions evaluated were:

(i) HcI

(2) SPC2

(3) HClAC2(IO0-N)C3

with H, A, N as above, and SP denoting fuel smoke point. These forms were

evaluated in a_ attempt to both globally represent the combustor parameter

response to chemical property variations and to discern particular fuel

property influences.

Detailed Ana]ysis of Dome Radiation Data

The radiation on _he dome of ghe ':ombustor was determined by use of

two transpiration radiometers. These cevices (described in Section V) were

mounted to place their sensing element flush with the combustor liner and

hence received the total (i.e., full hemispherical) radiation to that

location of the dome. One of these two radiometers performed consistently

throughout the test effort, providing repeatable values for tests w_th Jet

A-U fuel and duplicating the initial calibration. The data acquired with

this device (referred to as QDO_'J_Iin Table 14, the Appendix Data Tables,

and Comprehensive Data Report) were used to determine tLe fuel chemical

property influences on radiation. T_ second radiometer was not consistent,

witb values either higher or lower than QDOMEI obtained; the calibratic_

was not repeatable. Hence these data were not analyzed.

The variations of dome radiation for the several test fuels are

represented in Figs. 27 to 29 which display the data in terms of fuel

hydrogen, total aromatics or naphthalene content, respectively. Clear and

expected trends are observable in each figure, with increased radiation

levels obtained with lower chemical quality fuel. Used in this manner,

each of these properties is treated as a global indicator of the fuel

38
' ,

property influence. That is, the depicted hydrogen content dependence

(Fig. 27) also reflects variations in both total aromatics and

naphthalenes; it does not represent the influence of hydrogen content

alone. Similarly the total aromatics and naphthalene representations

include the influence of all other chemical property variations. As noted

earlier, aromatic hydrocarbons (benzenes and naphthalenes) display a high

propensity to soot. Hence it would be expected that increasing concentrations of these species would promote greater soot concentrations, raising

the emissivity of (and consequently radiative heat transfer from) the

combusting medium. The range of the hydrogen content variation principally

resulted from the range of the of benzene and naphthalene content

variations. Since these hydrocarbons have relatively low hydrogen content,

increasing concentrations of them reduced the fuel hydrogen content; hence

increased aromatics increased the radiation heat load while reducing the

reduced hydrogen. Of these three, the hydrogen content representation

correlated the data better than either toc_l aromatics or naphthalene

content. Significant scatter is observed in Fig. 28 indicating that total

aromatic content does not properly represent t_e chemical property

influences. Naphthalene content correlated the data well except for two,

low naphthalene fuels--tetralin and xylene tower bottoms (XTB). Tetralin

is a double-ring molecule produced by saturating one ring of naphthalene.

A principle pyrolysis product of tetralin is naphthalene (Ref. 38) and

therefore in the diffusive burning environment of the combustor, tetralin

likely behaves as a high naphthalene content fuel. Indeed, the radiation

level measured for tetralin was slightly greater than obtained for BLS, a

fuel with a naphthalene content of 30 pct. The XTB fuel consisted of I00

pct benzene-type hydrocarbons. High sooting rates would be expected, and

based on acquired data, were achieved. Hence naphthalene content alone

could not be expected to fully correlate all data.

It is noted, however, that the chemical properties of tetralin and XTB

were exceptional. Both were from the specialty products class of fuels,

.ith each composed entirely of a single hydrocarbon-type molecule.

Further, each of these hydrocarbons had a high propensity for sooting.

Twenty--one test fuels had compositions which included mixtures of single

ring and multi-ring aromatics (two other specialty product fuels were

purely paraffinic, decalin and UTRCI) which _panned the ranges: total aromatics, 2.5 to 76 (vol) pct and naphthalenes, 0 to 29.7 (vol) pct. Data

from tests with these fuels dominate the trends depicted in Figs. 27 to 29.

It is apparent that for these 21 fuels the naphthalene content was a

stronger influence on the radiative heat load (and hence on the soot

formation) than the total aromatic (or by difference, She single-ring

aromatic) content of the fuel. Furthermore, the dominance of naphthalene

content was established despite its content being a minor portion of the

total aromatics. Again, radiation levels for ERBLS3 with 30-pct

naphthalene content (76-pct total aromatics) were comparable to a I00 pct !

single-ring aromatic fuel (XTB).

As stated above, considering all fuels tested, hydrogen content was a

better global indicator of the chemical property influence than total aromatics or naphthalene content alone. Figure 30 depicts the variation in l

dome radiation with an acknowledged global fuel specification parameter,

39
smoke point. The data were well correlated by this parameter. In fact,

regression analyses indicated that smoke point correlated the data better

than hydrogen content:

radiation - H-1"65 R2 = 0.87

6'

radiation - SP-0" , R2 = 0.93

The latter regression is depicted in Fig. 31.

As discussed by others (e.g., Ref. 39) the smoke point is a good indicator

of the sooting tendency of a fuel. Hence the quality of the data fit is

consistent with the premise of changing chemical properties principally

affecting soot formation.

The influence of specific chemical properties was pursued by

examining the results of the parametric variation tests and of further

regression analyses of all data. Results from the parametric variation

tests are presented in Fig. 32 (which is an enlarged section of Fig. 27).

Mean values of the nine-point data set are depicted with brackets

indicating the extent of the data set standard error. The values in

parentheses are the hydrogen, total aromatics and naphthalene contents,

respectively. The following fuel combinations comprised the property

variations: hydrogen--ERBS and 7A; total aromatics--ERBS and 8A; napthalene--ERBS, 9A and 9B.

A relatively minor change in dome radiation was attained for the

hydrogen content variation. The mean value did increase with reduced

hydrogen content, but the overlapping limits of standard error prohibit

precise definition of the influence. Indeed, the error limits allow the

possibility of no influence of hydrogen content on radiation. While the

variation of hydrogen content might appear to be small (0.75 pct point), it

does represent 70 pct of the difference in hydrogen contents of Jet A rod

ERB$. Rence these results indicate that despite a significant variation of

hydogen content (at constan: single- and multi-ring aromatic content), no

statistically significant change in radiation would be expected. This

result is consistent with the actual fuel composition variation achieved in

these tests. As indicated above, the hydrogen variation arose from

exchange of normal- and cyclo-paraffius. Both of these saturate_ have low

sooting tendencies and hence no significant combustor influence would be

expected. This observed independence of radiation on purely hydrogen content emphasizes the global character of representations like that depicted

in Fig. 27. Used in this o-anner, hydrogen content variation represents a

variation of species more fundamental to the sooting p_ocess.

The domm radiation level also did not significantly vary for tests

performed with fuels offering a parametric variation of total aromatic

hydrocarbons. That is, despite a substantial reduction in this property,

the mean value of radiation reduced only slightly, with the limits of

standard error overlapping. The total aromatic variation was achieved by

exchanging saturated hydrocarbons for single-ring aromatics. Hence the

data indicate that benzene-like structures did not strongly contribute to

the radiation load. This result is in contrast to the high radiation

levels indicated earlier (Fig. 29_ for XTB, and the well established

4O

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sooting propensity of benzene-type molecules. The oifference in these

results may be due to the naphthalene content in the fuels. That is, the

variation in total aromatics was achieved at a constant naphthalene content

of 13.5 pct. As discussed previously it appears that naphthalenic

hydrocarbons present a dominant influence on the sooting process. At the

13.5 pct level, these structures may have overridden the single-ring

variation. Another total aromatic parametric variation was achieved in

tests performed with fuels ERBLSI and UTRC3B, both of which possessed a

naphthalene content of approximately 15 pct. Again, no significant

influence of total aromatics was observed. Further definition of the

influence of these hydrocarbons was sought via regression analyses of data

acquired for all fuels; these results are discussed below.

Substantial increases in the dome radiation were observed for parametric increases in the fuel naphthalene content over a range comparable to

the difference in this property for Jet A and ERBS. Since total aromatic

content was held constant, reductions of naphthalene content resulted from

substitution of single-ring aromatics for double-ring naphthalenes. Thus,

the lowest naphthalene content fuel, UTRC 9A, had the highest concentration

of benzenes in this fuel sequence, while ERBS had the highest naphathelenes

and lowe_t benzenes. The radiation level followed the naphthalene trend,

and hence decreased for increasing single-ring aromatics. This behavior

again demonstrated the importance of naphthalene conten_, reaffirming them

to be more influential than the benzenes. These data also indicate that

the naphthalene influence was non-linear. That is, most of the total

increase in radiation occurred for the first half of the total naphthalene

content change. Therefore slight increases in a low naphthalene content

fuel could result in disproportionate increases in sooting tendency, and

consequently in the radiation load.

Regression analyses were performed to discern specific chemical

property influences. Generally, data from tests with all fuels were used

to cover the wides range of fuel propertypyaF_ation, c_esults from analyses

using a three property parameter [i.e., H_ A_{100-N) _] indicated that

total aromatic content was not a significant correlating term; the data

were tracked equally well with or without its inclusion. The following

two-property parameter, which embodied both hydrogen and naphthalene

_ontent was the best representation of the data (See also Fig. 33):

radiation H-I"2(100-N) -0"4 R2 = 0.93

Four important features of this correlation were noted. First, both i

fuel property terms contribute significantly to the predicted change

of radiation. For example, for the property changes associated with Jet A

and ERBS fuels, half of the predicted radiation increase is attributed to

the hydrogen content decrease and half to naphthalene content increase. , i

Second, this correlation does not fully prescribe the influence of specific 1

chemical properties. As previously discussed, the change in hydrogen

content is a global indication of a more fundamental hydrocarbon-type !J

change. Its presence in this correltion compensates for many unknown i

chemical features such as the apparent interactive influence of benzenes

and naphthalenes. The regression analyses did, however, discern the I

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. important influence of naphthalenic hydrocarbons. Third, the quality cf

this correlation was equal to Chat for a smoke point correlation, both of

which were superior to a solely hydrogen content correlation. Hence, while

naphthalenes are recogni.ed as an important chemical property class,

smoke point--an existing fuel specification par_ueter--appears to proporly

prescribe the influence of fuel chemical properties. Fourth, none of the

correlations was a perfect fit to the data. Hence, for any two fuels the

three functional relationships--hydrogen, smoke point, hydrogen and

naphthalene--may overpredict, _.derpredict or perfectly-predict the

changes evidence_ by data. For example, the parametric property variation

test results indicated that naphthalene content variation was principly

responsible for the difference in radiation for Jet A and ERBS. Nave of

these three correlations reflects such a strong influence and hence all

underpredict the change in radiation. A user of regression analysis results

ought to recognize the implicit assumption that the trends established by

a large data set (e.g., twangy-five fuels) are more reliable than trends

indicated by a_ubset (e.g., two fuels) of the data. For ape, fect

ccrrelation (R_ _ I), thi_ issue is academic; for non-perfect (i.e., 2

realistic correlations) this issue _agnifies as the departure from R = 1

grows.

As asserted above, the chemlcal property influence on dome radiation

was similar to the influence discerned for exhaust soot. It was con'tuded

that the unifying influence on both was the level of soot produced in the

, dome region cf the combustor--increased soot producing higher emissivities

and hence greater radiation heat loans, and increased soot providing a

higher source _oncentration prior to its oxidation down to combustor

exhaust levels. In general, radiation heat transfer depends on both the

medium emissivity and its temperature. Since the calculated combustion

temperature of a fuel depends on its composition, with generally increasing

levels obtained for decreasing hydrogen content, a significant variation

in radiation might be expected only because of a temperature variation.

However in the test combustor, covtinuous radiation from soot particles

represented a major portion of the total radiative load and the temperature

of these particles may not be equal to the comhJsted gas temperture. That

is, the combustion of these particles will be controlled by diffusion of

oxygen to the surface, with the particle temperatures dominated by

stoiochi._etric carbon oxidation, modulated by the concentration of

oxidizer in and radiation exchange with the neighboring media. Temperature

measurements in the primary zone of auother model combustor (Ref. 40) using

the Kurlbaum technique indicated only a very small temperature change of "

the radiating source despite significant changes in fuel chemical

_ composition. Further, the temperature levels measured were essentially ;

. independent of the combustor fuel-a_- ratio. These observations support i

the concept of soot forming in a di._usion flame zone, and hence always in

near-stoichiometric fuel-air mixtures, and that the particles radiate at I

temperature levels associated with soot oxidation. If it is assumed in the

present program that the radiation source temperature also did not vary

with fuel composition or overall fuel-air ratio, then the observed changes

in radiation level must be attributed to changes in emlssi_ity, and hence

from changes in chemical property induced soot producti)n. This situation

is consistent with the observed similarity of chemical property dependences

# 42

.o

II

®
for the dome radiation and exhaust soot data. The emissivity levels can be

determined only if a temperature of the soot particles is assumed. The

measurements of Ref. 40, adjusted to the combustor inlet air temperature of

the current effort, indicate this temperature to be 2250K. Using this

value, and a Stefa_- Boltzmann relationship, the black body radiation level

would be 1450 kW/m_ and the e_issivity for any measured radiation level:

emissivity = dome radiation/1450

The data acquired spanned the general range of 300 to 700 kW/m 2 indicating

a corresponding emissivity range of 0.2 to 0.5.

Summary of Chemical Property Influence

Liner Tem9erature Rise and Smoke Number

Influences of fuel chemical properties were also evident in the liner

temperature ri_e and exhaust smoke number data.

The liner temperature rise parameter analyzed was the difference

between the combustor inlet air temperature and an average of ten liner

thermocou_les. The data obtained from the case-mounted radiometers indicated that the chemical property effects were concentrated in the dome and

first three louver re, ions of the burner. During the test program, several

of the original 39 liner thermocouples failed becaus_ of thermal or

mechanical stress. Therefore, the ten measurements used in the analyses

were confined to the dome and first three louver regions, and used thermocouples which existed for all tests. Eight of these were located either on

the dome or at the first axial position (slightly downstream from the

louver lip) on lo_vers 1, 2, or 3. The metal temperatures for these eight

locations would be influenced more by changes in the radiation heat

transfer than by changes in convective heat transfer. Hence the temperature rise parameter used reflected changes in the radiation heat load.

The smoke number data were obtained from three, ganged, smoke probes

at the combustor exist. Data acquired for any fuel indicated that the oxidation mechanisms within the secondary zone of the combustor dominated the

soot produ, ion mechanisms in the dome. As shown for ERBS fuel in Fig. 34,

as the combustor exit temperature increased (because of increased overall

fuel-air ratio) the smoke level decreased, despite an increasingly

fuel-rich primary zone. As observed for thu radiation data, there was not

a significant influence of fuel nozzle size (for the range of nozzle

numbers used fn this program) as smoke numbers for Jet A-U fuel were

similar for all injectors, except for smoke numbers acquired on a second

test day using a NN=32 nozzle. That is, data were acquired with this

nozzle on two test days. On one day the Jet A-U smoke numbers were consistent with values obtained on other test days (with other nozzles) while

values acquired on the other test day were lower. This difference was believed to result fronta bias on samplcs acquired the second test day.

Since other combustor parameters were simil_r for both days, it appears

43

]w
. that th_ bias was associated with the sampling process. The smoke numbers

acquired for the six fuels on the second day were adjusted by use of data

acquired for Jet A-U. In particular, the test fuel smoke numbers were

scaled in proportion to the ratio of the Jet A-U data acquired the second

test day to the Jet A-U data normally acquired.

The influence of chemical properties on the liner temperature rise

and exhaust smoke number were similar to those observed for the dome radiation. (Figures A-I to A-8 in the Appendix present the variation of these

parameters for Test Condition 2.) The variations of each were globally

represented by the fuel smoke point which was again found to be a better

correlating parameter than fuel hydrogen content alone. Plots of the

combustion parameters indicated that total aromatic content did not

properly represent the chemical property i_fluence while naphthalene

content was an important influence. As discussed for the dome radiation,

the liner temperature ri_e and smoke number data for tetralin and xylene

tower bottoms were not correlated by fuel naphthalene content. Results

from tests with fuels offering parametric variations of chemical

properties indicated that changes in either hydrogen and total aromatic

contents did not significantly affect either the liner temperature rise or

smoke number. The former result reflected the pure influence of hydrogen

content, and not an apparent influence because of changes in sooting

hydrocarbon structures. The insensitivity of the combustor parameters to

total aromatic content is believed to be associatd with the level of naphthalenes present in the fuels, as discussed in the presentation of the dome

radiation data. Regression analyses of dlta from all fuels again indicated

that total a-omatic content was not asta istically-significant term in the

correlaLion parameters investigated. The best correlating parameters

embodied two fuel properties, hydrogen content and naphthalene content, and

hence were improved global representations. This feature is depicted in

Fig. 35 which displays the excellent correlation betweell liner temperature

rise and the two property parameter. That the best correlation parameter

included fuel naphthalene content re-affirmed the importance of this

property.

Table 19 presents results from regression analyses of the dome radiation, liner temperature rise and smoke number data for all three test

conditions. These results were obtained from regressions performed in the

logarithm plane [i.e., log (dome radiation)] and hence differ slightly

from results presented previously which were optimized in the real plane.

For each variable, each regression parameter tracked the data similarly for

all three test_conditions; only a small variation in the exponents (CI, C2)

and quality (R') was observed. The similarity of the chemical property

influence on the radiation, liner temperature rise and smoke number data

discussed above were also reflected in these regression analyses by the

exponent quotient, CI/C2. The small variat:on indicated that hydrogen and

naphthalene contents had the same relative influence on these three

combustor parameters.

Particulate Size and Number DensitL

A characteristic size and number density of the soot exiting the i

!

44
t

burner on its centerline were determined from light scattering measurements. Data typically obtained for these measurements are depicted in

Figs. 36 and 37. As indicated, the particle size was invariant to

operating condition, with an 0.22 ± 0.02 _m particle size being indicated.

Indeed, the particle size determined for tests with any fuel, at any condition, was within these limits. This interesting result was not dictated

by the measurement technique as its sizing sensitivity has beem

demonstrated in a laboratory set up over a particle size range of 0.09 to

0.50 _m. As used, the measurement technique identified a single particle

size assumed to be representative of a size distribution. However, light

scattering signals are greatest for large particles, implying that the

characteristic size is biased toward the larger particles of the

distribution. Hence, the data indicate that a significant quantity of 0.22

_m particles existed f6r all fuels, for all conditions. The sizing

sensitivity of the scattering arrangement used would not be strongly

responsive to variations of the smaller particle sizes. Characteristic

sizes simile- to those observed in this program have been determined using

optical techniques for a variety of other burners ranging from a

ramjet-type dump combustor (Ref. 41) to a laboratory mono-disperse spray

flame (Ref. 42). In those instances (as well as in the present study) the

particles were far removed from the soot generation region and therefore,

as discussed in Ref. 42, likely were mature agglomerates of large numbers

(600-3000) of primary soot spheroids. The constancy of the particle size

indiated that it results from fundamental soot growth mechanisms in times

short compared to chose offered by a wide variety of burners with little

(if any) regard for fuel-type.

The soot particle number density decreased With increasing combustor

exit temperature, ogain indicating a vigorous oxidation mechanism in the

burner secondary zone. As observed for smoke number, the number density

responded to the fuel chemical properties, increasing for fuels with

greater propensity to soot (i.e., decreased smoke point). The constancy

of particulate size implied that a relation existed between soot numler

density and smoke number. Regression analyses for these data, for ail

fuels at all test conditions, resulted in the correlation depicted in Fig.

38:

lOgl0N = 4.9 SN0"082 , R 2 = 0.83

where N = Number density and SN = Smoke Number

While the quality of the correlation is only fair, the standard error of

the number density data indicated that further improvement was not

warranted. While a clear trend is indicated for the smoke number range

evaluated, it ought to be recognized that the trend must change for very

high smoke numbers. That is, by definition, the maximum smoke number is

i00. Therefore, in the coordinates of Fig. 38, the number density must

approach this limit with a vertical asymptotic character.

J

Soot was clearly being oxidized within the burner. Direct

observations within the burner using a fiber optic probe [activity

conducted under a NASA contract immediately subsequent to the experiments

t

45

I;

a

®
of this program (Ref. 43)] documented that the highly luminous, strongly

radiating media in the dome became transparent by the burner exit. The

axial distribution of radiation (Fig. 23) also documented this feature.

Soot formation and growth were limited to regions near the dome as farther

downstream the global equivalence ratio rapidly became fuel-lean. The

particle size and number density trends would indicate that the initial

soot number density was responsive to the fuel sooting tendency, with

decreasing concentrations along the burner because of oxidation. Data do

not exist to determine how the particle size varied. It would be expected

that small particles would be rapidly oxidized in accordance with the

"d-squared" law, with larger particle sizes reducing more slowly.

Combined, these processes could result in significant reduction in soot

while retaining sufficient numbers of larger particles to be interpreted as

a nearly constant particle size. Additional investigations are required to

acquire data on changing soot physical properties within a practical

combustor.

46

,

® J
SECTION Vlll COMBUSTO_ TEST RESULTS: CONFIGURATION-EFFECTS

A limited number of combustion tests were perforamed in an attempt to

determine changes in fuel chemical property influences because of changes

in the combustor airflow distribution. Two combustor configurations were

evaluated, one providing a reduced primary zone airflow and another

providing a greater airflow than the baseline burner used for the

fuel-effects tests. These two burners are described in Section III. At

the same overall fuel-air ratio, these combustors provided a leaner or

richer primary zone equivalence ratio (¢p), respectively, than the

baseline because of the altered airflow distribution. Tests were performed

at the three conditions defined in Table 16, resulting in the _ variation

indicated in Table 8. Note that the adjectives "lean" and "ric_" are used

in a relative sense. The primary zone was fuel-rich for all tests. Data

were acquired in tests with three fuels (in addition to Jet A-U): ERBS,

ERBLS2 and xylene tower bottoms (XTB). Because of the relatively few

variations (two configurations, four fuels) regression analyses were not

performed. Instead, general data trends were sought which permitted

interpretation of the configuration influences.

General Combustor Operation and Airflo_ Interaction

Both combustor configurations performed consistently, attaining a 99.9

percent combustion efficiency for all tests. Data acquired with Jet A-U

prior to combusting each test fuel were repeatable. The combustor exit

temperature pettern factor (PF) was nearly constant for each configuration,

but varled between configurations. For the baseline burner values for Test

Conditions I, 2, and 3 were nominally 0.12, 0.13 and 0.14, respectively.

For the lean configuration, values higher than the baseline were achieved

(PF = 0.17, 0.19, 0.23) while lower values (PF = 0.09, 0.09 and 0.I0) were

observed for the rich configuration. This trend was a result of the

technique used to alter the airflow distribution. The lean configuration

was acbieved by opening each of the six combustion air holes in louver 1

while closing the corresponding holes in louver 5. Hole diameter changes

were specified to maintain a constant liner open area, or equivalently,

constant liner pressure loss. Therefore, while additional airflow was

admitted to the primary zone, lesser airflow was available for tertiary

zone injection. Furthermore, the smaller diameter downstream holes reduced

the penetration of this airflow into the core flow. These two effects

reduced the mixing level and resulted in the observed increase in pattern

fac=or. The opposite trends held for the rich combustor configuration.

Less primary zone airflow provided greater tertiary zone flow, resulting in L

greater mixing and reduced pattern factors. This interaction of primary .

zone airflow and tertiary zone mixing was unavoidable for the simple

combustor configurations used.

The changing tertiary zone mixing behavior could significantly alter

the chemical property influences discerned in the fuel-effects tests. For

example, Fig. 39 depicts the smoke number data acquired for Test Condition

2 for each configuration. The fuel property variation is represented by

the smoke point. For this condition __ varied from 1.2 to 1.55. While the

expected trend of decreasing smoke number for lower sooting tendency fuels

(i.e., higher smoke point) is observed, the ¢ influence is opposite the

P

47

@
expected trend. That is, richer primary zones did not produce greater

exhaust soot. This contradiction is apparently the result of the tertiary

zone mixing behavior described above. Data for the highest _ were

acquired from use of the rich burner configuration, the devic_ with the

greatest tertiary zone mixing, while data for the lowest ¢ were obtained

with the lean combustor. The low smoke number values fromPthe rich

combustor indicate that the vigorous mixing enhanced soot burnout, a

behavior consistent with the strong oxidizing tendency noted in the

fuel-effects test phase. In those tests, it was observed that exhaust

smoke levels decreased with increasing overall fuel-air ratio despite

corresponding increases in the rich primary zone equivalence ratio. In

that case, the higher combustor exit temperatures promoted oxidation

processes which overcame the enhanced soot production in the primary zone.

For these configuration-effects data, the average combustor exit

temperature has equal for all three burners. The improved (i.e., lowered)

pattern factor indicated that fewer low temperature (and hence weaker

oxidizing) regions existed, resulting in greater soot burnout. The

opposite trend was true for the lean combustor. Despite primary zone soot

production levels lower than expected for the baseline, the lean burner

produced equivalent or greater exhaust soot concentrations. The degraded

mixing of this device rendered it inefficie_It at consuming the soot.

These data indicate that the rapid increase in soot emissions from use

of poor chemical quality fuel can be offset by enhanced particle burnout.

Uniformly high tertiary zone tempertures are optimal. If this condition is

achieved, a reduced chemical property influence can be experienced as

: evidenced by the relatively small smoke number variation over the range of

sooting propensities offered by XTB to Jet A.

Configuration Influences in the Primary Zone

The influence of changes in the combustor configuration on the primary

zone were represented by the dome radiation data. Two types of influence

were investigated: influence of variations of primary zone equivalence

ratio (_) at a constant test condition, and influences of variations of

test condition for constant _ . Data for the former case were obtained

from tests with each configuration operated to provide identical combustor

exit temperatures for each fuel (i.e., nearly identical fuel flowrates).

In the latter case, data were acquired in tests with the three

configurations operating at compensating conditions to achieve a nearly

constant _ . Hence, both the configuration and the test condition varied

in this sequence. These two variations can be viewed as variations along a !

column or along a positively-sloped diagonal, respectively, of the Cp !

values contained in Table 8. i

Data representing the influence of _ on the dome radiation level for

Test Condition 2 are presented in Fig. 40_ The open symbols denote the 1

normalized data acquired for the fuel variation represented by smoke !

point values. Radiation levels for the lean burner were consistently !

higher than for the baseline, while lower values were obtained for the rich i

configuration. Identical trends were observed for data obtained at Test i

Conditions 1 and 3. If all of the radiation heat load was produced by soot t

|

formed in the primary zone, the opposite trend could be expected. That is, l

as discussed previously, the soot appears to radiate at a relatively con48

b
stunt temperature because it is oxidized in a diffusion flame structure.

Richer _ could be expected to produce higher soot concentretions, resulting in h_gher emissivities and heat loads.

The observed trend in dome radiation suggested that a temperature

responsive effect was present. In particular, while the soot temperature

was insensitive to the equivalence ratio, the gas temperature was not. A

UTRC exponential wide-band model was used to calculate the radiation level

for the equilibrium gaseous species concentration which would exist for

each primary zone equivalence ratio. These gaseous radiation levels were

used to adjust the data to the values shown as solid symbols in Fig. 40,

which represent the variation of particulate radiation for differing ¢ and

fuel properties. The expected radiation increase for increased fuel P

sooting tendency is apparent. Of more interest, however, is the indicated

insensitivity of this radiation to equivalence ratio. This feature is

attributed to the constancy of the fuel distribution resulting from use of

the same fuel flowrete (for any fuel) with each configuration. The primary

airflow was varied for each configuration to produce the __ change.

However the swirler surrounding the injector was not altered and the liner

pressure ioss was held constant by specifying compensating hole diameter

changes in louvers I and 5. Therefore, the airflow expected to impose the

principle influence on the fuel spray was invariant. It appears that while

the globa% equivalence ratio did vary, the fuel pattern (or equivalently

the fuel concentration) did not. Hence the diffusion flame structure in

the primary zone would remain constant producing similar soot levels for

these configurations. Gaseous combustion products apparently did mix with

the p,imary airflow, with greater radiation loads produced in the higher

temperature, lean burner (_ = 1.2) than for the baseline configuration.

Differing levels of dome radiation were observed for equivalence ratio

v_tlations in the fuel-effects tests. In those instances, however, the

variation was achieved by altering the fuel flowrate. These

configuration-effects results indicate that the fuel-effects ¢ influence

likely resulted from a differing fuel distribution in the primary zone.

Unfortunately, data do not exist to specify this alteration. Such a change

is a real effect, however, that could be experienced in other burners usin_

pressure-atomizing injectors. Combustors using air-blast nozzles would be

expected to show less sensitivity to his phet,omenon as the fuel distribution would be dominated by the airflow patterns. It is restated that at

any one condition, the combusting zone structure was similar for all fuels.

Therefore data acquired at any condition could be consistently compared for

fuel-effects or configuration-effects. The alterations imposed by changing

fuel flow i_nvalidate similar analyses of data from multiple conditions, i

These configuration-effect test results also indicate that the global i

value, ¢ , does not always adequately represent the important features of , I

the primary zone. For the configuration-effect tests, radiation levels de- !

creased with increasing _p; in the fuel-effects tests, radiation levels increased with increasing __. The manner in which the variation was achieved !

dictated the result. Thi_ feature is further illustrated in the data I

presented in Fig. 41, which depicts the variation in dome radiation for

changes in test condition but at an approximately constant primary zone I

equivalence ratio. Differing levels of radiation were observed,

re-affirming that ¢_ does not fully describe the primary zone behvior. The I

data were acquired _rom tests with the three configurations. However, each i

was operating at a different test condition and, consequently, at a i

t

49 1

l

.. 1
different fuel flowrate. Fuel distribution differences likely existed,

resulting in the observed spread in radiation heatload. Note that tLe

highest radiation levels were consistently achieved for the lean burner

which operated at Test Condition 3. Tile highest dome radiation levels in

the fuel-effects tests were also obtained at this condition but with a

global value of CD = 1.7. Indeed, the levels obtained for the _p = 1.4

tests were higher-(as indicated by the comparison on Fig. 41) because of

greater gaseous radiation. This influence is identical to that

demonstrated in Fig. 40, and indicates that the concentraticn of any

individual fuel is a strong influence in determining the combustor

radiative heat load. For each configuration (or equivalently at each

condition), the data for all fuels follow nearly identical trends. That

is, the fuel chemical property influence for each configuration was

similar, the same result observed in the fuel-effects tests.

r

t

i

i

I

i

I

!

I

I

i

!

5O I

!

!

I

i

I

®
SECTION IX CONCLUSIONS AND RECOMMENDATIONS

Based upon the data acquired in the combustion test program the

following conclusions have been made:

I. The influence of changes in fuel chemical properties on a gas turbine

combustor are properly represented by changes in the fuel smoke point,

a specification parameter.

2. Fuel naphthalene content is a strong contributor to gas turbine

combustor radiative heat load and exhaust soot emissions.

3. The size distribution of the agglomerated soot particles exiting a gas

turbine combustor is adequately represented by a characteristic size

of 0.2 _m. This size does not depend on fuel chemical properties.

4. The strong oxidizing character of a gas turbine combustor can be used

to offset potentially increased soot emissions from use of a lower

chemical quality fuel if high mixing rates are achieved in the

secondary and tertiary zones.

5. Fuel concentration patterns in a gas turbine combustor primary zone

strongly influence the quantity of soot produced, and therefore alsc

the radiative heat load.

6. Fuel oxidiation in the primary zone of a gas turbine combustor is

controlled by diffusional processes and is therefore not always well

represented by a global equivalence ratio.

It is recommended that investigations be conducted to address the

following technology needs as indicated in this program: I

I. Development of fundamental mechanisms and models of soot production

from aviation-type fuels.

2. Data to document the soot particle size, size distribution and number

density within a gas turbine combustor.

3. Data to quantify the contribution of single-ring aromatic structures

to fuel chemical property influences on a gas turbine combustor.

4. Data to separately define the fuel chemical and physical property

influences on a gas turbine combustor at low-power operation.

' 5. Data to identify changes in chemical property influences associated !

with the use of air-blast fuel injectors in gas turbine combustors.

6. Development of models and acquisition of data to determine the

atomization and distribution of fuel sprayed into a gas turbine E

combustor operating at a high-power condition.

51
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[

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Suppressant Fuel Additives on Engine and Test Cell Exhaust Gas

Opacities. Naval Postgraduate School Report NPS-67-82-004, May 1982.

42. Bonczyk, P. A. and J. J. Sangiovanni: Optical and Probe _easurements

of Soot in a Burning Fuel Droplet Stream. UTRC Report UTRC83-25 i

(submitted to Combustio_ Science and Technology), June 1983.

I

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43. Morey, N.: Personal Communication. [

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t-- _.. r-- C_ r--- t_ 0 ._" O_l 0 0 0

•_ 0 _-- ,-'-" ¢xJ _0 C_

• i
- TABLE 3 - Parametric Variations of Chemical Properties

Blend Prope ties

Aromatic Naphthalenes

Fuel Component (vol fraction) H (wt pct) (vol pct) . (vol pct)_

Hydrogen Variation

[RBLSI ERBS (0.79) 12.35 38.4 16.6

Blending Stock (0.21)

: UTRC2A JP7 (0.533) 11.87 34.9 16.0

Methyl naphthalenes (0.175)

Xylene tower bottoms (0.189)

Decalin (0.103)

ERBS ERBS (I.00) 12.95 28.4 13.5

UTRC7A JP7 (0.660) 12.53 26.2 14.9

Methyl naphthalenes (0.149)

Xylene tower bottoms (0.118)

Decalin (0.073)

Total Aromatic Variation

ERBLSI As above 12.35 38.4 16.6

UTRC3B Jet A (0.60) 12.41 24.9 14.5

No. 2 (0.I0) i

Methyl naphthalenes (0.15)

Decal in (0.15)

ERBS ERBS (I.00) 12.95 28.4 13.

UTRC8A JP7 (0.75) 12.o4 16.5 13.4

Methyl naphtha.enes (0.15)

Decal in (0.I0)

Naphthalene Variation i

_ ERBS ERBS (I.00) 12.95 28.4 13.5

. UTRC9A Jet A (0.50) 12.89 30.7 1.5

JP7 (0.20)

, Xylene tower bottoms (0.20)

r Decalin (0.I0)

UTRC9B Jet A (0.40) 13,10 30.1 7.3

Nc. 2 (0.45)

ERBS (0.10)

Xy!ene tower botto-:s (0.05)

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TABLE 6 - Combustor Open Area Distribution

Area Distribution (cm_

Section _lumbe_______[rDiameter (mm__) Area

Dome Cooling 60 1.78

(4 rings) 60 1.47 60 !,47

60 1.09 4.09

Louver 1 Cooling 96 1.98 2.96

Combustion 6 12.7 7.13

Louver 2 cooling 96 1,98 2,96

Combustion 6 12.7 7,13

Louver 3 Cooling 96 1.98 2.96

Combustion 6 12.7 7.13

Louver 4 Cooling 96 1.98 2.96

Louver 5 Cooling 48 1.98 1.48

Combustion 6 12.7 7.13

Louver 6 Cooling 48 1.98 1.48

.o,_ w

- ........ 1984009339-07(
TABLE 7 - Liner Effective Area Distribution

Effective _a (cm2) Percent of Total

Sect_____iion Individual Adjusted (with Swirler)

Dome Cooling 3.2 3.0 8.1

Louver 1 Cooling 2.65 2.5 6.8

Combustion 4.90 4.6 12.5

Louver 2 Cooling 2.65 2.5 6.8

Combustion 4.91 4.6 12.5

Louver 3 Cooling 2.57 2.4 6.5

Combustion 4.76 4.5 12.2

Louver 4 Cooling 2 81 2.6 7.1

Louver 5 Cooling 1.25 1,2 3.3

Combustion 4.90 4.6 12.5

Louver 6 Cooling .40 1.3 3.5

Sum of Components 36.0 33.8 91.8

Measured Total Liner 33.8

Swirler 3.0 3.0 8.2

Total Liner with Swirler 36.8 36.8 I00.0

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TABLE 8 - Primary Zone Equivalence Ratio

Variation for Jet A

Overall Fuel-Air Ratio O.Cl5 0.018 0.022

Overall Equivalence Ratio 0.22 0.26 0.32

Combustor Configuration (Airflow Split) Primary Equivalence Ratio

Lean (0.23) 0.98 1.18 1.44

Baseline (0.195) 1.18 1.42 1.74

Rich (0.17) 1.31 1.57 1.92

D

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. TABLE 9 - Fuel Atomization Levels

Fuel Nozzle No, 35

Fuel Temperature = 295 _+5K

_Fu____l SMD (um)/IncludedCone Angle (deg)

Fuel Weight Flow (kg/hr)

ll8 133 162

JP4-S 41/70 26/65 8/60

JP4-A 44/70 25/65 7/60

UTRCI 44/70 30/65 13/60

JP4 45/65 27/65 8/60

AFAPL 53/75 35/70 21/65

GMSO 55/75 45/70 23/65

JP7 56/70 40/65 18/60

UTRC 9A 56/75 41/75 14/65

JP5 58/75 46/70 24/65

Jet A 60/75 39/70 20/65

UTRC 7A 60/70 47/70 19/65

UTRC 8A 64/75 47/75 21/70

UTRC 2A 64/80 47/75 22/70

DF2 64/70 48170 26/65

XTB 65/75 52r70 26/65

UTRC9B 66/70 51/70 16/65 i

ERBS 68/70 47/70 20/65

UTRC3B 69/75 48/75 28/70

BLS 73/75 55/75 37/70

ERBLSI 74/75 55/75 22/70

ERBLS2 74/75 48/75 22/70

ERBLS3 74/75 54/70 2b/70

AFAPL 6 83/75 55/70 22/65

Decalin 83/75 63/70 42/65

Tetralin 83/75 67/75 45/70 i'
TABLE I0 - Fuel Temperature Influence on Atomization

Fuel Nozzle No. 35

-Fue__ll Fuel Temperature SMD {um)/IncludedCone Angle (deq)

(K)

Fuel Weight Flow (kg/hr)

118 133 162

Jet A 299 60/75 39/70 20/63

311 53/75 38/70 23/65

328 31/70

Tetralin 299 83/75 67/75 45/70

311 90/80 78/75 49/70

328 83/80 68/75 45/70

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®
. TABLE II - Fuel Nozzle Number Influence on Atomization

Fuel Temperature = 298K

Fuel -Nozzle Number SMD (_m)/Included Cone Angle (deg)

Fuel Weight Flow (kg/hr)

83 96 118 133 162

Jet A 35 - - 60/75 39/70 20/65

30 - - 30/70 21/65 -

20 29/65 15/60 - -

' Tetralin 35 - - 67/75 45/70

30 - - - 46/70 26/85

20 - - - 12/70 -

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TF..3LE12 - Fuel Nozzle Specificatiun

Fuel SMDfor NN=35 Test Nozzle SMD for

(_m) (NN) Test Nozzle (_)

JP_-S 26 40 39

JP4-A 25 40 38

UTRC1 30 40 45

JP4 27 40 41

AFAPL 2 35 35 35

Gh.0 45 35 45

,IP7 40 35 40

UTRC9A 41 35 41

JP5 46 35 46

Jet A 39 35 39

UTRC7A 47 32 36

UTRC8A 47 32 36

UTRC2A 47 32 36

DF2 48 32 36

X,B 52 32 39

UTRC9B 51 32 39

ERBS 47 32 36

U_RC3B 48 32 36 ..

BLS 55 32 42

ERBLS 1 55 32 42

ERBLS2 48 32 36

ERBLS3 54 32 41

AFAPL 6 55 32 42

Decal in 63 30 39 ,

Tetral in 67 30 42 '

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TABLE 13 - Airflow Influence on Atomization

Fuel Nozzle Nu. 35

Fuel Temperature = 298K

Fuel Swirler Airflow Differential SMD (_m)/Included Ccn_ Ar,gle .(deg)

Pressure Fuel Weight Flow = 13S kg/hr

(kPa)

Jet A 0 42/70

4.92 33/55

26.2 4/45

Tetralin 0 67/75

4.92 59/60

26.2 13/45
ORDINAL PAGE

, TABLE 14 - Test Fac;lity Instrumentation OF POOR QUALITY

Symbo_ Measurement Description

_ev i__..__ Ra_

PVAUP P/T 2.7 MPa Air pressure upstream of venturi

TVAUP I/C Type K Air temperature upstream of venturi

PVATH P/T 2.0 MPa Air press,lreat throat of venturi

TVENT T/C Type T Venturi body temperature

PHTREX P/T 1.7 MPa Air pressure at electrical heater exit

PFPUMP P/T 5.9 MPa Fuel pressure at pump discharge

TFPUMP T/C Type K Fuel temperature at pump discharge

PFINJ P/T 6.9 MPa Fuel pressure in line entering rig

TFINJ T/C Type K Fuel temperature at nozzle

WF Micromotion -- Fuel mass flow

FUEL FLAG MV -- Indicatcr of fuel valve actuation

P31 P/T 1.7 MPa _ir pressure at combustor inlet, R = 5.7 cF

P32 P/T 1.7 F;P_ Air "essureat combustor inlet, R = 3.8 cm

{ P33 P/F 1.7 F,Pa Air pressure at combustor inlet, R = 1.9 cn_

P34 P/T 7 MP Air pressure at combustor inlet, R = l.O cm

T31 T/C lj_e K Air temperature at combustor inlet, R = 2._ cr

T32 T/C Type K Air temperature at combustor inlet, _ = 5.0 cr:

; T33 T/C Type K Air temperature at combustor inlet, R = 2.5 cTT34 T/C Type K Air temperature at combustor inlet, R = 5.0 c:"

PCASEi _/T 1.7 MPa Liner airflow pressure, Z = 9.2 cm

PCASE2 P/T 1.7 MPa Liner airflow pressure, Z = 20.3 cn_

PCASE3 P/T 1.7 MPa Liner airflow pressure, Z = 31.4 cm

TLOI060 T '_ Type K Liner temperature along ow

- TL62G60 (13 to_l), e = 60 eg

TLOII80 '._ Type K , e : 180 deg

- TL62180

TLOI300 T/C Type K , e : 300 deg

, - TLC2300

. PRADN2 P/T 3.4 MPa Nitrogen pressure upstream of venturi for

transpiration radiometers i

TRADN2 T/C T"pe T Nitrogen temperature upstream of venturi I

PRADI P/T 1.7 MPa Nitrogen press' re in radiometer, _ = 90 deg I

' PRAD2 P/_ 1.7 MPa Nitrogen pr_;sure in radiometer, e = 300 deg }

; TCRAD! T/C Type T Radiometer coolJnt temperature, e : _0 deg I

TCRAD2 T/C Typ_ T R_diometer coolant temperature, e = 300 deg I

• QDOMEI mv -- Signal from transpiration rad,ometer, _' = 90 de_ I

QDOME2 mv -- Signal from transpiration radiomc 2r. ;- = 300 dc I

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I
oRIGINAL P_,fL;"S"

. _F POOR QUALiI_ TABLE 14

(Continued)

RADI mv -- Signal from themlopile radioneter, Z = 9.2 crRAD2 mv -- Signal from thermopile radiometer, Z = 14.8 c_

RAD3 mv -- Signal from thermopile radiometer, Z = 20.3 c_

T401-T422 T/C Type B Gas temperature at combustor exit

P4 P/T 1.7 MPa Gas pressure at combustor exit

PNFFI mv Photomultipliertube output for scattered

light at 45 deg from forward

PHT2 my Photomultipliertube output for scattered

light at 135 deg from forward

LPOWER mv Laser powermeter output

TCRI T/C Type T Coolant exit temperature, ring l

TCR2 T/C Type T Coolant exit temperature, ring 2

TCR3 T/C Type T Coolant exit temperautre, ring 3

TCR4 T/C Type T Coolant exit temperature, adapter spool

TCTC T/C Type T Coolant exit temperature, T/C rake

TCXl T/C Type T Coolant exit temperature, emissions rake

TCSNIN T/C Type T Coolant inlet temperature, smoke probe

-' TCSNEX T/C Type T Coolant exit temperature, smoke probe

FXl P/T 1.7 MPa Gaseous sample pressure

TXl T/C Type K Gaseous sample temperature

PSN P/T 1.7 HPa Smoke sam_,e pressure

UHC FID Signal from UHC analyzer

RUHC mv Signal UHC analyzer range

02 Paramagnetic Signal from 02 analyzer

R02 mv Signal denoting 02 analyzer range

NOX Chemiluminescent 3ignal from NOX analyzer

RNOX mv Signal denoting NOX analyzer range

CO NDIR Signal from CO analyzer

RCO mv Signal from CO analyzer range

C02 NDIR Signal from C02 analyzer range

RC02 mv Signal denoting C02 analyzer

NOTES:

I. P/T = pressure transducer, strain gauge

2. T/C = thermocouple

3. All P/T readings with range = 1.7 MPa performed with a single pressure scanner

• 4. Coordinate reference position -

R is the radial coordinate with R = 0 on combustor axial center line

Z is the axial coordinate with Z = 0 at _!;ecombustor dome flange

e is the azimuthal angle about the axial center llne (clockwise positive

viewing downstream) with e = 0 through the igniter locatica

5. SAE smoke filter samples manually obtained; no interface with data system

6. Liner temperature nomenclature: TLXXYYZZZ

where XX = louver number, TT = T/C position, ZZZ = e

! ®
TABLE 15 Emissior, s Analysis Instrumentation

ORIGINAL FAGE I:_

OF POOR QUALITY

Instrumer, t

! Instrument Error '.

Component Range _Detection Method Ful I ScaI e

THC 0-I ppmv Flame lonization Detector ± 5.Off

Intermediate ranges ± 1.0_

_ O-10,_ ± 1. Ot

NOx 0-2.5 ppmv Chemiluminescence Detector _+1.0"

Intermediate ranges (6) TECOModel IOA ± 1 0c

0-I0,000 ppmv ± l.Of

CO 0-200 ppmv Nondispersive Infrared

0-I000 ppmv Beckman Model 865 ± 1.0%

0-5000 ppmv

CO2 0-2_,: Nondispersive Infrared ± 1.0 C

0-5% Beckman Model 315 ± I.OL

0-15% ± 1.0%

02 O-l_J Paramagnetic Analyzer ± l.OC,.

0-5 _- Scott Model 150 ± 1.0 _

0-I0% __1.0

0-25% ± 1.0 c

V
J

TABLE 16 Test Conditions

Condition 1 Condition 2 Condition 3

Combustor upstream air pressure (MPa) 1.32 1.32 1.32

Combustor upstream air temperature (K) 700 700 700

Combustor total air flow (kg/s) 1.84 1.84 1.84

Combustor ideal exit temperature (K) 1246 1346 1473

D

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ORIGINAL PAG_ _a7

OF POOR QUALITy

TABLE 17 - Measured or Berivcd PerformanceParameters

Parameter Correction Precision

Txpe Technique Assessment

Airflow rate M* ....

Fuel flow rate M* ....

Burner entrance average total pressure M* ....

Burner entrance average total temperature M* ....

Fuel manifold oressure M IC X

Fuel injector pressure drop C Eqn X

Fuel temperature at injector M -- X

Fuel-air ratio metered C Eqn X

Average combustor exit total temperature M IC X

Average combustor exit static pressure M IC X

c Average combustor exit total pressure C Eqn X

Combustor total pressure loss C Eqn X

' Primary zone flow split * ....

Primary zone fuel-air ratio C Eqn --

Primary zone flame temperature C Eqn --

" " Combustor liner temperature M IC X

Combustor thermal radiation flux M Eqn X

Emission indices, CO, UHC, NOx M Cor X

• Percent CO2, 02 M IC X

Average SAE Smoke Number M -- X

Combustion efficiency - aT C Eqn X

" Combustion efficiency - emissions C Eqn X

Combustor reference velocity C Eqn X

Sample-line temperature, pressure M ....

Burner exit pattern factor C Eqn X

Fuel-air ratio - emissions C Eqn X

Symbols: M - Measured

C Calculated

- Eqn - Corrected v_lues obtained as equation results using corrected

" parameter values

, IC - Corrected by use of influence coefficients I

Cor - Corrected by use of correlation relating derived and measured !

F

, parameters

* - Test parameter i

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_ _.,
TABLE 18 Local Equivalence Ratio

Test Condition

1 2 3

Overall Equivalence Ratio

0.22 0.26 0.32

Local Equivalence Ratio

Combustor Section

Primary zone 1.2 1.4 1.7

Louver 1 1.2 1.4 1.7

Louver 2 0.8 1.0 1.2

Louver 3 0.5 0.6 0.7 :

i

NOTE: (I) Baseline combustor configuration

(2) Lquivalence ratios are for Jet A

-w
OmOINAL

OF POOR QUALITy, TABLE 19 Regression Analysis Result_

Variable Condition Regression Form R2. Cl C2 CI/C2

Dome 1 Hcl 0.83 -I .5

Radiation 2 0.87 -1.7

3 0.84 -I .4

1 SPC1 0.92 -0.4!

2 0.91 -0.43

3 0.92 -0,36

1 Hcl (IO0-N) C2 0.87 -1,4 -0.47 3.0

2 0.92 -1.5 -0.30 3.0

3 0.91 -1.2 -0.54 2.2

Liner 1 Hcl 0.84 -0.57

Temperature 2 0.78 -0.56

Rise 3 0.68 -0.42

1 SPcl 0.92 -0.15

2 0.90 -0.15

3 0.89 -0.12

1 HC1 (100-N) c2 0.90 -0.50 -0.20 2.5

2 0.90 -0.47 -0.25 1.9

3 0.81 -0.33 -0.24 1.4

Smoke 1 HC1 0.81 -I .7

Number 2 O.78 -2.0

3 0.76 -2.3

1 SPcl 0,93 -0,50

2 0.84 -0.57

3 0.91 -O.67

1 HC1 (100-N) C2 0.88 -1.6 -0.62 2.6

2 O.J6 -I .7 -0.75 2.3

3 0.81 -2.0 -0.64 3.1

*These anlyses performed in Io9 plane (i.e., log (radiation)).

Similar quality expected in real plane. l

m

km

. o,
,¢

R84-915908-29

ORIGINALPAGE |_

OF POOR QUALITY

,oo r_ IDEAL CORRELATION

..J

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u3 80 -- .,#' _'-BLS (CORR) o,I

I-- / (MEAS, O9

< /

rr

ILl 60 - i0

" O

O

_ UJ

<°_ >- 40 - //0/0

_o

1--

O 20 -

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0 20 40 60 80 1O0

TOTAL AROMATIC BY FlA. ASTM 1319 (VOL PCT)

4-

Fig" 1 Comparison of Total Aromatic Content for Two Analysis Techniques

L

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83-7-29-1 l'

- i

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R84-915908-29

ORIGINAL PAGE ;_

OF POOR QUALII'Y

30 BLS (CORR) _._' J'j_

/

>: O /

n- _1o ,

I.--

W BLS (MEAS) J

z_

o /

,.,- /

r-_ O

" O p- 20 - / LUO

- _o C_, /

<>

..

O4

>.. _ IDEAL CORRELATION

rnm /

,,,'_

•, ,,, ._j _ lo - /

•, < /

I--

I

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1

: 0 I I .

0 10 20 30

f NAPHTHALENEBY UV SPECTROPHOTOMETFIY,

: ASTM1840(VOLPCT)

l

Fig. 2 Cor;,_)arison of Naphthalene Content for Two Analysis Techniques

83-7-29-2

®
R84-915908-29

i,i

ORIGINAL PAGE 191'

OF pOOR QUALITY

83-7 -29-3 ¢

iP
',,.:.,4 J

e.

R84-915908-29 ORIGINAL PAGE _3

OF POOR QUALITY

a) SIMPLEXPRESSUREATOIvllZINGINJECTOR

e'

b) AIRFLOWSWlRLER

Fig. 4 Fuel Nozzle and Air Swirler

82--199--B 83--7- 29-4

I;
R84-915908-29

m

ORIGINALPAG2 _'3

OF POORQUALITlf

IV &P

• MANOMETER

BOARD

, d°l°l°il°L! _ , ooo o

AIR SUPPLY _

o o o o

CHOKED

VENTURI I

Fig. 5 Test Setup for Effective Are: Determination

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R84-915908-29 ORIGINALPAGF.",,

_F POOR QUALITY

%

%,.

•-"-. \ ....

"o

\

\

PROBE

• [:

,_ COMBUSTOR WALL

O:_ENCIRCLES SET 1 1Z' 7{m DIA

CLOSED CIRCLES _ET 2

(b) SAMFI_ING TUBE LAYOUT

; Fig. 6 PrimaryAirflow SamplingProbe

B3 7 29- 6

. ®
R84-915908-29

ORIG, 'AL p,e_CZ;_

OF POOR QUALITY

'COMBUSTION

SWIRLER

5'3

SYM PROBESET AZIMUTH ,i

¢

O I ON HOLES

ID 2 ON HOLES

40 1"3 1 BETWEEN HOLES O ID

_" IE 2 BETWEE_,_HOLES CD

IX_-X DEN BURNEr OTESCUMULATIVE" r A(pct)

-F

c 30 tb

'3

n D if) 20- m

_.J

tr- I

10-

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0 2 4 6 8 10 12 14

POSITION ALONG CAN, crn

A,

f,

Fig. 7 CalculatedCombustor Airflow Split I

I

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R84-9_ 5908-2_

ORIGINALPAGE I5_

OF pOOR QUALITY

80

JET

I

Fig. 8 Predicted Droplet Lifetime in PrimaryZone with 20 pct TurbuPence

83-7-29-7

bm

-=a
t*_j4,-

R84-91 5908-29

a

ORIG,N,-,,_"_'" - : ' "

OF POO#OUALtTY

4P

AIRREGULATED S,JP#_ t

JET A

{UNDEt4,..GROUND -

STORAGE

..._ CANISTEu MICROMOTION

MASS FLOW METER -- P . &=

3.WA _, M Z_NC,t,'£- E;-

TEST FUEL NOZZLEISWIRt ER /

(20 hle,'_ / \

\\ ',"

MALVERN P_,_TICLE

SIZE ANAl Y_R

I

. Fig.9 FuelSprayCharacterizationFacility

83-'/-29-8

ira,
R84-915908-29

ORIGINALPAGEt8'

OF POOR QUALITY

0.2

WF {Kglhr)

O 133

0 162 JETA FUEL

0.15 - M _,

• o /_\% so%--.

- ,Z\'_ o__Ass\

FLCVV "_ ;

o.1- __ I "'-"

0 05 " -..

0 • _'_"

1.0 0.5 0 0.5 1.0

NON-DIMENSIONAL RADIAL POSITION, r/R

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Fig. 10 Fuel SprayMass Distribution for No. 35 Nozzle ,

;

1

{

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R84-915908-29

ORIGINAL PAGE|_

OF POOR QUALITY

I

SURFACE TENSION .,,_l-_,_im_ INERTIA FORCES

DOMINATES _ DOMINATE

I

I

200 -

_CPANFIELD (REF 21_

/ rUTRC PRESENT EFFORT,

A loo- I

50 -- PARKERHANNI_IN

>-- (REF 20 22_

<_

it

03

I "SAG _"S.EAR

10 I BREAKUP I BREAKUP I

0.1 1.0 10 100

WEBER NO.

Fig. 11 Weber Number Regimes i

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83-7-29-9

Ill,

ta
" R54-9" 5998-2_'

ORIGINALPAGE IS

OF POORQUALITY

0 i g I i ......... i

NO 35 HAGO NOZZLE

FUEL TEMP = 295 K

W F = 133 Kg/hr O

• 60 -

-0 0 0

g 0 0

50-

_ 0

_" 0

40 - I_

: 0

30 - O

o8

20 I I ,.

20 25 30 35

SURFACE TENSION (dyne/cm)

Fig. 12 Influence of Fuel Surface Tensionon Measured Atomization

_" 83,- 7-29- I0
R84-915908-29

ORIGINALPAGE |,_

OF POOR QUALITY

0 ' • i , , , • i

NO 35 HAGONOZZLE O

FUELTEMP= 295 K

WF= 133 Kg'm 0

60--

0 0 0 0

0

5o- o

:_c_ O00_ 0 0

0

>-

0

rrt'3.. 40 O

oo O ;_

O i.

30- 0

g

20- ! ! I , . i I

0 1 2 3 4 5 6

VISCOSITY (cst)

Fig. 13 Intluence ot Fuel Viscosity on Measured Atomization !

1

83-7-29-11
R84-915908-29

ORIGINALPb,&_r"j

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BACK

PRESSURE

VA_.VE

I I

I TEST AND I

AIR PREPARATION I INSTRUMENTATION I EXHAUST

SECTION I SECTIONS I SECTIONS

I I

I I

l

Fig.14 Aviation.FuelPropertyEffectsTest Facility v

b

; i!

, t

I

)

i

I

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I

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61 --6--64--4 1

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_-_
.,_ +

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0

81 --6-64_ 7

=

iml,'

," (_o

_ ' .
R84-915908-29
R84-915908-29

t,

OF POOR QUALITY

a) PROBE BODY

d

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.... . .. ,_,, _.._;_,_.,m,_._i..l_,¢T..¢,_%...." -,, i

b) TIP SCREEN i

{

!

i.

Fig. 17 TranspirationRadiometer ,!

I

!

!

I

t

_t 8822-292--A -B !

83-7 _9- 12 l
,e

R84-915908-29

ORIGINAL P/_GL: ._@

OF POOR QUALI='W

6OO

"41----- HEAT LOAD

0 _)0 0

E 400- 0

g 0

_ 0

_ X

-J

b.-

< ^ - 15

UJ V

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o 0

TEMPERATURE RISE

: 5< 200-

r,- O _"

- 10 "_

0

O ,

! "

- 5

, 0 I I I

' 4 6 8 10

i NITROGENMASSFLUX(gmlseclcm2) 1

Fig. 18 Operational Characteristics of Transpiration Radiometer

82-11-38-1
R84-915908-29

.r

ORIGINg, L F.s:_G__,.

OF POOR QUALITY

Y

,L

t,,) EMISSION SAMPLE INLET (20 TOTAL) RAKES AT X = ,- 1 58, _ 4 44 cm

O TYPE BTHERMOCOUPLE f22TOTAL) RAKES A_' y= -,-1 02, ±305, -'-_5 0_ cm

" X SMOKE SAMPLE INLET (3 TOTAL) INLETS AT X= _305, y=203cm

X=000 y=-203 cm

: Fig. 19 Probe Distribution at Combustor Exit

81-11-23-1

ml,
®

R84-915908-29

- ORIGINAL I'_-,(;,_ :,f_

OF POOR ,QUALITY

100 - i

I

I

I

I

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\

'-4

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n=l 94- 0661

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i

'/ i

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L i'

1 I I I t

0.1 0.2 0.3 0.4 0.5 }

PART'CLF D! _,METER(#m) i

I

-- Fig. 20 Scattered.Light Ratio Dependence on Particle Diameter I

83-7-29-13 I

1

"1l (i5 ;•
R84-915906-29

ORICD" ,_ PAC'L ._,

OF POOR QUALI'i"Y

4" '_LITPuT TO LOCK-IN AMPL.I_IE_

\

: _PMT

pM T

\

-- _ p

• (-) 0 ASSEMBLY

, /..,& LIGNME N:

, _____C _ j WINDOW

L

F

,. ©

A APERTURE

AL ARGON-ION LASER

C MECHANICAL CHOPPER

F NARROW BAND OPTICAL FILTER AND POLARIZER

L LENSE

P NITROGEN PURGE

PM POWER METER

PMT PHOTOMULTIPLIER _'

PR POLARIZATION ROTATOR

W WINDOW b

i

l

-- Fig. 21 Layout of Particle Sizing Apparatus i

t

i

81-6-64-17
.,e

R84-91 5908-29

,- ORIGIrJALP;v.'.[,_;,_

OF POOR QUALi'I'_

700

600 -

NOTE EACHSYMBOLREPRESENTSA DIFFERENTTESTDAY

E 500-

z

O

Itr

"' LIJ, 8

' ._0 400- Z_

OF] r,

Dr_ D

t_

0 b,a

300 -

200 i I i

30 32 35 40

NOZZLENUMBER(NN)

,1 I 1 . I I ,

1.0 1.5 2.0 2.5 3.0

, RELATIVEATOMIZATION SMD(NN)/SMD(NN= 30)

Fig. 22 Variation of Dome Radiation for Jet A.U Fuel

83-?-29-22
..,r' (t)

R84-915908-29

ORIGINS!. p;:_&;]f:_'

TEST OF POOR OUALI'_" FUEL CONDITION

0 JET A-U I

n ERBS 1

0 ERBS 2

"_ A ERBS 3

125

100 -

_ 75-

0

Z

_ 50-

Z

I I I

LOUVER LOUVER LOUVER

25- _ 2 3

I I I , J

00 5 10 15 20 25

AXIAL DISTANCE ALONG COMBUSTOR (cm)

; {

Fig, 23 Axial _tstribution of L}nerRadiance for ERBSFuel

83-7-29-23

m
®

R84-9t 5908-29

ORIGINAL t:qiO, ._ [_,..

- OF POOR QUALITY

900

140 t 0 LOUVER

1'3LOUVER2

_' LOdVER3

... 800 -

0

120 -

0

700 -

0 0

0

0

• _ 100 -

E

: ._" 600 - 0 C_ 0 0 0

_ O0

LU 0

0 _ 0

z,<o O O

O O O0

_ Q El

a: 80 - 500 -"

LLI

Z

.._m []

, •

LJ

13 D

,oo_ 80- 41, _ _

• [] ;

300 - _ • ;

_ ,

i

"-" 40-

J

|

!

200 1 I I | I

9 10 11 12 13 14 15

HYDROGEN (wt pct)

t

.t Fig. 24 Variationof Liner Radiancefor Test Condition 1

v

83-7--29--24
R84-915908-29

,_ _j

OF POOR _bALIT'Y'

9OO

140 [] r'l 0 LOUVER I

• [] LOUVER 2

• LOUVER 3,

800 -

A

0 J_ • •

120 - • •

70( - I_ O 13

[3

0

E_oo- '-' • _

• _ 60( - 0 •

"' o _> 0 0 0

z

_< o 0 o

0

,< 0 0 0 0

a: o o

rr 0 O 0

,,, 80 500-

Z

0 o 0 0

0

0

400 -

60

300 -

i

i

40

200 , I I I | i

• 9 10 11 12 13 14 5 [

, HYDROGEN (wt pct) Ii

' i

I

Fig. 25 Variation of Liner Radiance for Test Condition 3 !

!

83-7-29-25 t'

. 1

,_, ;.
R84-915908-29

ORIGINAL PAGEi_

OF pOOR QUALITY

CONDENSATION REACTIONS _ ,1 "" II _ SOOT

l

_TC_._._ l I

I I

_, PARE ,T AROM _x'_- I I

HYDROCARBON _G_, I I

', _. I J

SOOT _ SOOT

: PRECURSOR

ALIPHATtCS

Fig. 26 Active Sooting Mechanisms for Aviation Fuels

!

83-7-29-26
- R84-915908-29

OF POOR QUALITY

7oo

IDTET

_XTB

600 - _BLS

_ERBLS3

_ERBLS2

500-

e,J __RBLS1

E qti3s

17A ERBS

9B

Z

•, O _DF2

•AF6

fm •DEC

< 400- n,-

" uJ •9A

• AF2 JP5

O • •GMSO

• JET A

•JP4A

jP7 9 • JP4

IPJP4S

300 -

_q

2O0 I J I I I

9 10 11 12 13 14 5

,, HYDROGEN(wt pct)

Fig. 27 Dependence of Dome Radiation on Fuel Hydrogen Content for Test Condition 2

83-7-29-27

lip
R84-915908-29

. ORI_,,'-I,-_LPAGE IS

OF POORQUALITY

700

TET( )

XTB( )

600 -

_BLS

OE_B_S?

_ERB_S: E

5O0 -

Z O3 B OERBLS' O

< RBS

08A O_B

ODF2

rr

uJ OAr6

', _. ,DEC

O

D 400

.: GMSOO OJP5

_JET A

OJP4A

;. QJP4

O JP7 I_JP4S

. 300 -

I

200 I I I I

"J 0 20 40 60 80 100

TOTAL AROMATICS (vol pct)

, Fig. 28 Dependenceof Dome Radiationon Fuel Total Aromatic Content for Test Condition2

83-7- 29-28

., _'
R84-915906-29

ORIGINAL PAGE i_

OF POOR QUALITY

70O

ITET

4 XTB

600 BLS_

ERBLS3

04

E •ERBLS2

500

" ZO • 3B • ERBLS:

___ •7A

, < •ERBS

F, •gB • 8A

< •DF2

13:

IJJ •AF6

o0 40: IDEC

•AF2

GMSOO • JP5

• JET A

•JP4A

ejp4

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300

)1

P

i

." 20[. I 1

0 10 20 30 i

NAPHTHALENE (voI pct) t

i

; !

,' [

I

Fig. 29 Dependenceof Dome Radiation on Fuel Naphthalene Content for Test Condition 2 i

i

I

i

83-?-29-29 I

• l

g -
L.-:r. ,.- R84-91 u_08-2'9

ORIG!N,C.LPAGE i5

OF POOR QUALIT_

700

• TET

• XTB

600 Q BLS

• ERBLS3

• ERBLS2 E

_ 500

Z EBBLSI • • 7A

O

-- 3B9B•••

,,_ EBBS

• 8A

DF2•

rr • AF6 I,.U

• DEC

0

: (D 400 -

9A •

• AF2

• JP5

JETA • • GMSO I

": JP4A • J

JP4S

3O0

• 1

J

--- 200 : .,, .I, I

.- 0 10 20 30 40

SMOKE POINT

I

}

Fig. 30 Dependenceof Dome Rsdla|ion on Fuel Smoke Point for Test Condition2

|

!

t

83--7--29-30 1

-' l

w
., ®

R84-915908-29

ORIGINAL PAGE _9

OF POOR QUALITf

700

TET

XTB

R2= BLS

600 -- •

O ERBLS3

E •

ERBLS2

• -_ 500 -- 7A

Z • ERBLS_

._ O ERBS

BA •

< DF21_ 9B

< DEC •AF6

rr •

"' 400 -- 9A

• O JP5 2 •

, _ GMSO•

O JET A

: •JP4A

; 300 _

200 JI ' I I

0.1 0.2 0.3 0 4

Sp-0.6

t

" i

Fig. 31 Correlation of Dome Radiationwith Smoke Point for Test Condition2

" i

• I

1

i

i

84--1--104--4 i

. l

-- t
,eR84-915908-2'2

ORIGINAL P_,,G_". _.:_,

OF POOR QUALITY

5OO

7A (12 5.26 2 149)

ERBS (13 0.28 4. 13 5)

c,J

450 -- 9B(131 301 73)

' ,

• _ 8A(128. 165 134_

Z

O

d3 400 -

rr

l.lJ

9A(129 307 1 5) JETA'(137, 159 1 9) O

°

350 - tr

3O0 I 1 I ,.

12.0 12.5 13.0 13.5 14 0

HYDROGEN (wt pct)

Fig. 32 Influence of ParametricFuel PropertyVariations on DomeRadiation for Test Condition 2

a

- "/-29-31 l

,b 83

P !

i

I
®

R84-915908-29

• ERBLS3

ERBLS2

E

' _ ,500 ERBLS:

3B•

Z

O 9B E_BS _.. 7A

< DF2 •

, R •

<

or" AF6 •

uJ DEC •

O 400

tm JP5 • -3_ AFZ

GMSO•

• JET A

- • JP4A

JP45

_ 300 --

I

200 I I I I I

. 0.6x10 2 0.7 0.8 09 1.0 1 1 1 2

H-1 2 (100.N)-0.4

Fig. 33 Correlationof Dome Radiationwith Fuel Chemical Properties

for Test Condition2

84-1-104-2
R84-915908-29

a

ORIGINAL Pl.i.,c =._

OF POOR QUALll_'

40

O

30 -

uJ

• m

:_ 0

D 0

Z

"' 20 -

v

0

O3

iii

10 -

0 , I I ,

1200 1300 1400 1 i00

COMBUSTOR EXIT TEMPERATURE (K)

Fig. 34 Influence of Operating Condition on Smoke Number for ERBS Fut}I

83- 7- 29- 32

Ill'

1
R84-915905-29

ORIGINAL F,,_..: i,_

0." POOR QUALI]qf

400

350

Y

,. uJ XTB 0'3

IJJ

rr ERBLS2 •

Z) ERBLS2

< 300 ERBS ERBLSl

rr •

• ILl _2A

n A_6

• 3_

ELI AF2 •_,:; 7_ t-- JP5

rr

uJ JP4A

Z •DEC

_ jp,,' JET A

- GUSO

. 250 JP7

1

200 I J "

0.08 0.09 0.10 0 11 !

i

- H "0'46 (100-N) "0 26 i

t

!

r

Fig. 35 Correlationof LinerTemperatureRise with Fuel Chemical Properties

,, for Test Condition2

84-1-104-3

Im

,,l!f
,j ®

R84-915908-29

ORIGINALPAGE lf_

OF POOR QUALITY

0.5

0 ERBS

_ JETA

04 -

t-

_ 9

E 03 -

I:i::

111

I---

_ o

E, o.2- _O CD

111

o

I2 ff

" _ 01 -

0 1 1

1200 1300 1400 1500

COMBUSTOR EXIT TEMPERATURE (K)

Fig. 36 Influence of OperatingCondition on Particulate D:ameterfor ERBS Fuel

I

:

83-1-29-33

-j
R84-915908-29

ORIGINALPAGE '_

OF POOR QUALITY

.,,1P

108

O ERBS

/k JET A

E 107 -

>-

I..-

Z

• uJ

_rru.l _o 0_

m _ 0

_ 10 6 --

_ Z

2

lo5 I 1 ,

1200 1300 1400 1500

COMBUSTOR EXIT TEMPERATURE (K)

I

Fig. 37 Influence of Operating Condition on Particulate Number Density for ERBSFuel

i

r

I

t

t [

I

|

I

I

!

i

I

83- ?- 29- 34" {

/

I
R84-9!5908-29

105.... I 1 I I

' 0 20 40 60

SMOKENUMBER

Fig. 38 Soot Number Density Correlated with Smoke Number

83-7-29-35

tm
R84-915938-2£

ORI_WAL FP.GE f-_

OF P :OR QUALITY

60

CONGFIGURATION _F

O LEAN 1 20

O BASELINE 1 40

50 - ,.., 0 RiCH 155 []

40-

rr

uJ

, t"n

z 30- o %

L W

o D

, 0 0

: 20- 0

10 -

0 ; I I I

0 5 10 15 20 25

" SMOKEPOINT

Fig. 39 Influence of Combustor Configuration on Exhaust Smoke Number

83-7-29--14

lip
.t., ®

R8 _-915908-29

• ORifilhlAL " " r,-"..... -, CONFIGURATION ep

D LEAN 1 2

OF POOR QUALITY O BASELINE14

0 RICN 155

700 O

OPEN SYMBOLS-TOTAL RADIATION

O SOLID SYMBOLS-PARTICULATE RADIATION

6OO

O o

O

E 500-

_: • 0

z0• 0

0

0

• uJ 400 - _ O

O

r, _ O

r

, !

300

t

200 I I I I

3 5 10 15 20 25

SMOKE POINT

Fig. 40 Influence of PrimaryZone Equivalence Ratio on Dome Radiationat Test Condition 2

83-7-29.36
!

f.

.; R84-915908-29

",_

ORIGINAL PAGe. i_

OF pOOR QUALII_

700 -

TEST

CONFIGURATION _p CONDITION

" D I LEAN 1 4 3

4_

• • BASELIN 1 4 2

'_ RiCH 1 3 1

D BASELINE 17 3

600 •

D

E 500

• -5

D

-": z0 _ •

< In

oc

"' I

. _ 400 -

O

O

300 -

t

b

i

I l I I

"',' 2000 5 10 15 20 25 !

" SMOKE POINT {

l

, i

I

!

Fig. 41 Influence of Combuslor Confi0m.,tion on Dome Radiation

I

: t

, . 83.7-29.37 I

t
APPENDIX - DATA TABLES

a

This appendix presents data which supplement the discussion of fuel

chemical property influences. A complete tabulation of all data is

contained in the contract Comprehensive Data Report. The following data

are presented in two forms. First, three tables, one for each test

condition, display the normalized combustor parameters obtained for each

test fuel. Second, as referenced in Section VII, plots of liner temperature rise and exhaust smoke number at Condition 2 are presented with fuel

., hydrogen, total aromatic, or naphthalene contents or smoke point as

independent variables.

Appendix Tables

I. Normalized Data fo_ Test Condition 1

2. Normalized Data for Test Condition 2

3. Normalized Data for Test Condition 3

Appendix Figures

A-I Dependence of Liner Temperature Else on Hydrogen Content at

Condition 2

A-2 Dependence of Liner Temperature Rise on Total Aromatic Content at

Condition 2

A-3 Dependence of Liner Temperature Rise on Naphtha]ene Content at

Condition 2

A-4 Dependence of Liner Temperature Rise on Smoke Point at Condition 2

A-5 Dependence of Exhaust Smoke Number on Hydrogen Content at Condition 2

A-6 Dependence of Exhaust Smoke Number or Total Aromatic Content at

Condition 2

A-7 Dependence of Exhaust Smoke Number on Naphthalene Content at

Condition 2 _J

A-8 Dependence of Exhaust Smoke Number on Smoke Point at Condition 2

|

Appendix Symbols

D Characteristic soot particulate diameter (vm)

\ F/A Overall combustor fuel-air ratio (--)

N Soot particulate number density at combustor exit (cm-3)

mp

8
- PHIP Primary zone equivalence ratio

QDO_I Radiation to dome radiometer (kW/m 2)

QCASEI Equivalent full-hemispherical radiation at Louver I (kW/m2)

QCASE2 Equivalent full-hemispherical radiation at Louver 2 (kW/m2)

_ QCASE3 Equicalent full-hemispherical radiation at Louver 3 (kW/m2)

SN Exhaust smoke number (--)

' TP Liner temperature rise parameter (K)

| , •
,

_o,o,,=o,,_o=.._©o._r.-.-_oo,_,._,=0=_o, ORIGINALPAG;_I-_

(NNOe_.'O_N•=.-0oN•C'_•N

0N_•,,.

_•NN•NN• rV• NN•C• _..•o_,•.qN•N•N_•

••••• OF POO

R QUALITY


R84-915908-29

m

ORIGINALPAGE i_

OF POOR QUALITY

400

..-. 350-

,v"

uJ

U'_ BLS

XTB •

• _ ERLBS3

I,-.- • ERLBS2

, <: •

300 -- ERLBS1 ERBS

"J • 9B 2A l 1 • DF2 • _ 8A •

3B 7A

• AF6 _• AF2

rr" 9A • JP5 • JP4A LU

Z • • • JP4S

: ._ DEC JET A GM_O 1 • J_

: 250 -- JP7

1

200L I I I I I

9 10 11 12 13 14 5

HYDROGEN (wt pct)

" Fig. A.1 Dependenceof LinerTemperatureRise on Fuel HydrogenContent

for Test Condition2

I.

I83-?-29-19

OB

tJ
R84-915908-29

ORIGINALPAG_ |9

OF POOR QUALITY

400

350 -

Y _BLS

XTBd

iii

03 Tel q

I:l: _ERBLS3

UJ •ERBLS2

(:z- D 300

I-- 3B •ER-oR£ • ERBLS1

<LLII:I: AF6_ ',Aeg 3 ZA

O. •BA DF2 •_k;2

_ua •9A

i-- IGMS O

)DRC -- Pdl_JcT A

gJ A _. •JP4A

Z '_JP7 --JP4S

m 25' -

I)I

200L I 1 I i :',

0 20 40 60 80 00 '"

TOTAL AROMATICS (volpct)

Fig. A.2 Dependenceof Liner TemperatureRise on Fuel Total Aromatic Conlent

for Test C,andition2

31_ 84--1--104--1

1
+Lt)

de

R84-915908-29

ORIGINAL PAGE IS

OF POOR QUALITY

400

350-

v"

LU

U)

X"rB

uJ D BLS

rr • TET ERBLS3

ERBLSF_ •

n- 300- 3B 2A

; UJ ERBS •

n 9B

L:_LI AF2 AF6_ • • 7A ERBLS1

I- 9A • DF2 8A

t"r _ _ JP5

LU I_EC O JET A

Z JP4A IO_MSO

•-.J 250JP4 0Dj:; S

1

2O0 I I

0 10 2O 3O

NAPTHALENE (vol pct) _"

i

Fig. A.3 Dependence of Liner Temperature Rise on Fuel Napthslene Content

- tor Test Condition 2

I

[

[

I

i

I

i

83-?--29-20 I

imp

- i
R84-915908-29

ORIGINALpAGE 19

OF POOR QUALITY

400

350 -

u.J BLS

oo XTBO •

rr"

TET • uJ

tr • ERBLS3

E3 • ERBLS2 I,--

< 300-

uJn tr ERBLSI_2A _ _ID OERBS 9B DF2

'_ 7A A • AFE

I.,u 8A ql

p- AF2 JP5

n- 9A •

uJ JET A •

Z • GMSO JP4

-'; JP4A _1t DEC O • O

250 - JP4S jP7

lq

200 I I I

0 10 20 30 40

SMOKE POINT

Fig. A-4 Dependenceof LinerTemperatureRise on Smoke Point

for Test Condition2

83--'/-29-21

bl
R84-915908-29

ORIGINAL PAGE {S

OF POOR QUALITY

60

XTB

50 - •

TET

BLS ERBLS3

@ @ • ERBLS2

40-

• ERBLSt

rrLu •

rn 2;-

'_ 3B • 8A

z 30 - • _ ERaS

LU 7A 9A

_, • DF2

' O • 0• JETA :_ 9B

09 •AF2 • • GMSC

• AF£ JP5

20 - DEC j_-

• •

JP4A :,

JP4 1

O@

JP,_S 10 -

0 1 I , I I I

0 10 11 12 13 14 15

HYDROGEN(wt pct)

4-

FIg. A-5 Dependence of Smoke Number on Fuel Hydrogen Content

•' for Tes! Condltlon 2

83.,-7-29-15

"" i
Lt;

R84-915908-29

" oRIGINALp_.,GEI3;

OF pOORQUALITY

6O

50 - XTe

TET

ERBLS2 ERBLS3 BLS

40 -

ERBLS"

2A •

a: •

_ 3B =

m

3_ 8A •

::3 • •gA z 30 -- _F6

UJ

,. _" _ DF2

_;O JE_A ERBS%9E

O3 GMSO•• ,_A AF2 JP5

Ill)DEC

20IOJP7 • JP4A

1 JP4

JP4S 1

o I 1 _ I

0 20 40 60 80 100

TOTAL AROMATICS (vol pcl)

Fig.A-6Dependenceof SmokeNumboron FuelTotalAromatics

for TestCondition2

1'

83---7-29-16

ml.

p ...... ®
11

R84-915908-29

ORIGINAL PAGE !2

OF POOR QUALITY

6O

4"

X'T,B

5O

• mET

ERBLS2 ERBLS3

• • BESt

40 -- ERBLS't

rr

" LU • 2A

L-,r3 3B

9A •

::3 8_ 1 ERBS

z 30 - • AF6 •

LU • • DF2 7A

E JET A AF2 9E•

O GMSO• •

03 • • JP5

) DEC

20-

JP7

JP4A

1

i_ JP4

JP4S 10-

o . I 1

0 10 20 3O

NAPTHALENE (VOL PCT)

Fig. A-7 Del)endenceof Smoke Number ol, Fuel Naplhalene Content

tot' Test Condition 2

t

* 83-7-29-17

lit

.. ®
R84-915908-29

ii

OR_GINALPAC,¢.;_, _ "

OF POORQUALIT_

60_

50 • X'rB

TET •

BLS

ERBLS3 P ERBLS2

40-

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zuJ 30 - 7A _ BS• AF6

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• GMSO

20 - .ip4A DEC

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JP4 •

#

JP4S 1

10-

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0 i I I L

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SMOKE POINT i

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Fig.A-8 Dependenceof Smoke Numberon Smoke Point for TIII Condition 2 !

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: 83-7--29-18 1_

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