NASA CR- 17 4848

R85AEB014

Analytical Fuel Property

Effects — Small Combustors

Phase II

Contract No. NAS3-22829

Final Report

By

LU

J. Monty and T. Scott

CL,

GO

2? MAH1985

SMM.I DOUGLAS

RESEARCH & ENGINEERING LWRARY

ST. LOUIS

Prepared For

National Aeronautics And Space Administration

Lewis Research Center

210OO Brookpark Road

Cleveland, Ohio 44135

GENERA L «^ ELECTRI C

Aircraft Engine Business Group

Lynn, Massachusetts
1. Report No.

CR 174848

2. Government Accession No.

4. Title and Subtitle

Analytical Fuel Property Effects - Small Combustors - Phase II

7. Author(s)

J. Monty and T. Scott

9. Performing Organization Name and Address

General Electric Company

Aircraft Engine Business Group

1000 Western Avenue

Lynn, MA 01910

12. Sponsoring Agency Name and Address

National Aeronautics and Space

Washington, D.C. 20546

Administration

3. Recipient's Catalog No.

5. Report Date

March 1985

6. Performing Organization Code

8. Performing Organization Report No.

R85AEB014

10. Work Unit No.

11. Contract or Grant No.

NAS3-22829

13. Type of Report and Period Covered

Contractor Report

14. Sponsoring Agency Code

15. Supplementary Notes

Project Manager, Stephen M. Riddlebaugh

NASA Lewis Research Center, Cleveland, Ohio 44173

16. Abstract

A test program was conducted to study the effects of non-standard aviation fuels on a typical

small gas turbine combustor, and to evaluate the effectiveness of design changes intended to

counter the effects of these fuels. This study was a follow on to an earlier analytical study

to predict the fuel effects and generate the design modifications evaluated in this program.

The T700/CT7 engine family was chosen for both studies as being representative of the class of

aircraft power plants desired for this study. Fuel properties, as specified by NASA, are

characterized by low hydrogen content and high aromatics levels. No. 2 diesel fuel was also

evaluated in this program.

The tests demonstrated the anticipated higher than normal smoke output and flame radiation

intensity with resulting increased metal temperatures on the baseline T700 combustor. Three

new designs were evaluated using the non standard fuels. The three designs incorporated

enhanced cooling features and smoke reduction features. All three designs, when burning the

broad specification fuels, exhibited metal temperatures at or below the baseline combustor

temperatures on JP-5. Smoke levels were acceptable but higher than predicted. This was partly

due to the increase in baseline combustor smoke levels with the broad spec fuels being higher

than anticipated.

One combustor of the three clearly demonstrated the best smoke and metal temperature

characteristics. It was also easiest to manufacture and incorporate into a production

design. GE with NASA's concurrence selected and subjected this combustor to a final component

test program.

17. Key Words (Suggested by Author (si)

Jet Fuels Fuels Properties

Aviation Small Combustors

Non-standard

ERBS

18. Distribution Statement

Unclassified - Unlimited

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price*

Unclassified Unclassified 39

* For sale by the National Technical Information Service, Springfield, Virginia 22161

NASA-C-168 (Rev. 10-75)
TABLE OF CONTENTS

PAGE

SUMMARY 1

INTRODUCTION 2

Broad Specification Fuels 2

Motivation 4

COMBUSTOR DESIGN DESCRIPTION 5

Concept 1 - Reverse Flow Convection Cooled Combustor (RFCC) 7

Concept 2 - Dilution Flow Impingement Cooled Combustor (DFIC) 14

Concept 3 - Impingement Cooled Replaceable Shield Combustor (ICRS) 16

COMPONENT TEST RESULTS AND DISCUSSION 17

Overview & Summary 17

Profile and Pattern Factor 20

Smoke 26

Metal Temperatures 30

Gaseous Emissions 32

Flame Radiation 34

Overspeed Protection - LBO Performance 34

Lightoff/LBO Performance 37

Idle Efficiency 38

OVERALL RESULTS 39
LIST OF FIGURES

FIGURE

NO. TITLE PAGE

1 T700 Engine Cross Section 1

2 Fuel Aromatics vs Hydrogen Content 4

3A Baseline T700 Primerless Combustor Cross Section 6

3B Baseline T700 Combustor with Thermocouple Installed 6

4 T700 Engine Smoke Characteristics 7

5A Reverse Flow Convection Cooled Combustor Cross Section 9

5B Reverse Flow Convection Cooled Combustor 9

6A Dilution Flow Impingement Cooled Combustor Cross Section 10

6B Dilution Flow Impingement Cooled Combustor 10

7A Advanced Airblast and Production Fuel Injector Cross Sections 11

7B Advanced Airblast Fuel Injectors and Production Fuel Injectors 11

8A Impingement Cooled Replaceable Shield Combustor Cross

Section 12

8B Impingement Cooled Replaceable Shield Combustor 12

9 Comparison of Shortened Inner Shroud and Standard

Inner Shroud 13

10 Patternator Results of Advanced Airblast Injector 15

11 T700 Heavy Duty Test Rig 17

12 The "George" Gas Analysis System 18

13 General Electric Smoke Cart 18

14 Schematic of Particulate Measurement System 19

15 Profile and Pattern Factor, Baseline Combustor (Max Takeoff) 21

16 Profile and Pattern Factor, RFCC Combustor (Max Takeoff) 22

17 Profile and Pattern Factor, DFIC Combustor (Max Takeoff) 23

ISA DFIC Combustor, Profile and Pattern Factor, Production vs

Advanced Airblast Fuel Injectors 23

18B DFIC Combustor, 12th Harmonic, Production vs Advanced Airblast Fuel Injectors 24

ii
LIST OF FIGURES (Continued)

FIGURE

NO. TITLE PAGE

19 Profile and Pattern Factor Comparison Before and After Modification 25

20 Profile and Pattern Factor, Modified DFIC Combustor, Three

Fuels, Max Takeoff 25

21 Profile and Pattern Factor ICRS Combustor, Max Takeoff 26

22 Smoke vs Baffle Face Fuel-Air Ratio - Overall GE Experience 27

23 Particulate Based Smoke vs % Hydrogen, Four Combustors 27

24 ARP 1179 Smoke, Max Takeoff, Four Combustors 28

25 NASA Smoke Results vs Baffle Face Fuel Air Ratio 29

26 First Panel Metal Temperature vs % Hydrogen, Four

Combustors, Max Takeoff 31

27 Emission Index NO vs Hydrogen, Four Combustors, Takeoff 33

A

28 Emission Index CO vs Hydrogen, Four Combustors, Max

Takeoff 33

29 Flame Radiation vs Hydrogen by Weight Percent, Four

Combustors, Takeoff 35

30 Lean Blowout Fuel Air Ratio vs Hydrogen by Weight Percent 36

31 Modified DFIC Combustor, Advanced Airblast Fuel Injectors,

Lightoff Performance 37

iii
LIST OF TABLES

TABLE

NO. TITLE PAGE

1 Broad Spec Fuel Properties 3

2 New Concept Approach Matrix 8

3 Predicted Maximum Metal Temperatures - Three Prototype

Combustors, ERBS 11.8 vs Baseline Combustor on Jet A 14

4 Relative Evaluations of Three New Concepts 20

5 Tabulated Raw Smoke and Baffle Face Fuel Air Ratio Data 28

6 Peak Metal Temperatures, of 4 Combustors, 3 Fuels All Panels 31

7 Peak Metal Temperatures, Modified DFIC Combustor 32

8 Gaseous Emissions and Idle Efficiency - Dilution Flow

Impingement Cooled Combustor 35

9 Tabulated Radiation Data 36

10 Tabulated Lightoff Data 38

iv
SUMMARY

The T700/CT7 engine is a front drive turboshaft or turboprop engine (Figure 1)

in the 1500-1800 shp (1120 -1340 kW) class as currently configured with highpower core flows of about 10 Ib/sec (4.5 kg/sec). It employs a straight-through

annular combustion system (Figure 3A) less than 5 in. (12.5 cm) in length

utilizing a machined ring film cooled construction and twelve low-pressure air

blast fuel injectors. Commercial and Naval versions employ two 0.5 Joule

capacitive discharge surface gap igniters.

The combustor employs a primary zone which responds to aromatics fractions

carried in the fuel in terms of smoke and flame radiation. The primary zone was

developed to provide a balanced trade-off between acceptable cold day ignition

and non-visible smoke. In-as-much as smoke requirements are relatively relaxed

for small diameter plumes, the primary zone stoichiometry for this application is

richer than that found in larger engine applications.

T700 DESIGN

INLET PARTICLE

SEPARATOR

CONTROLS & ACCESSORIES

TOP MOUNTED

THROUGH-FLOW

ANNULAR

COMBUSTOR

RUGGED

AXI-CENTRIFUGAL

COMPRESSOR

SELF-CONTAINED

LUBE SYSTEM

AIR-COOLED

GAS GENERATOR

TURBINE

UNCOOLED

POWER TURBINE

Figure 1. T700 Engine Cross Section
The three combustor concepts selected in Phase I were built and tested on JP-5 ,

#2 Diesel, and the two NASA ERBS fuels (12.8, and 11.8). They were evaluated

with respect to:

*Smoke

*Metal Temperatures

*Profile and Pattern Factor Effects

*Gaseous Emissions (Carbon Monoxide, Unburned Hydrocarbons, and

Oxides of Nitrogen)

* Complexity and Manufacturability

The DFIC Combustor was selected on the basis of superior test results to

undergo final parametric evaluation including:

*Profile and Pattern factor

*Smoke

*Metal Temperatures

*Gaseous Emissions

*Idle Efficiency

*Overspeed Protection LBO Performance

*Lightoff/LBO Performance

The effort performed in Phase II of this program applies only to a T700/CT7

engine family type combustor functioning in the engine as defined and does not

necessarily apply to other cycles or combustors of differing stoichiometry. The

program was not extended to any of the fuel delivery accessories such as pumps

or control systems, nor was there any investigation of potential systems problems

which might arise as a consequence of abnormal properties such as density which

might affect fuel schedules or aromatics content which might affect fuel system

seals.

INTRODUCTION

Phase II of the Fuel Property Effects - Small Combustors program was carried

out to evaluate the combustor designs recommended in Phase I by means of

testing actual hardware.

The three combustor concepts recommended in Phase I were designed to offset

the effects of low hydrogen, high aromatic fuels. Two effects were identified in

Phase I as being major problems - excessive smoke and excessive metal

temperatures.

Broad Specification Fuels

Table 1 shows the specifications of the three broad-spec fuels evaluated in this

program. Two of the fuels are ERBS blends - ERBS 11.8 and ERBS Jet Fuel

(12.8). ERBS 12.8 represents a likely jet fuel product from a synfuels process
TABLE 1

Broad Spec Fuel Properties

Spool I'ic.-i I ions KHH S 12. K

Composition:

Hydrogen, wl'i, 12.64

Aromntios, vol'i 29.8

Sulfur, Metvaptnn, wt'(. *0.003, max

Nitrogen, Total, wt'(.

Naplhalciic.s. vol'i. *i:i . inin

UyilruuiirUuM ooiiipositiuiinl

iiiidlysis

Volatility:

Distillation Temperature, °F

Initia l boiling point

10 Percent

50 Percent

90 PCrocnt

Fiiiiil boiling point

Residue, percent

Loss, percent

Flashpoint, °F

Gravity, API (60°F)

Gravity, Specific (GO/GU°1" )

Fluidity:

Freezing point, °F -50

Viscosity, @ -10°F, CS 6.58

Viscosity, @ +80°F, CS *2-3

Combustion:

Lower Heating Vuluc, Btu/lb 18,160

Thermal Stability:

JFTOT, breakpoint temperature, °F 492

(TDK, 13 max; and p, 25 mm)

•Proposed vnluc , not actually lusted

•• Deviates from oripnal spec

» 2 Diesel

NASA

13.01

318

3G-I

417

520

598

12C

.S423

394

430

514

604

162

.8514

-5 (Pour Pt.)

18,311

489

ERRS 11.8

11.64

481

22.95%

245

301

421

584

G 14

104

•.863 ± .002

-45

14.34**

•2-3

17,870

410 min'
oc

50

o

CL

30

20

10

0 L

TYPICAL REGRESSION

OF BROAD SPEC FUELS

EXPERIENCE AT

GENERAL ELECTRIC COMPANY

11 12 13

HYDROGEN BY WEIGHT PERCENT

14

Figure 2. Fuel Aromatics vs Hydrogen Content

such as shale oil or solvent refined coal. ERBS 11.8 (11.8% hydrogen by

weight) represents a worst case broad spec fuel. Number 2 Diesel was chosen

for the third fuel for several reasons. One is that it represents a very likely

real world substitute for JP5. The other is that it may show up secondary fuel

effects from characteristics other than % hydrogen. These characteristics would

be higher boiling range and lower thermal stability.

The ERBS fuels differ from common JP fuels and JET-A in that they have a very

high aromatic content (up to 48% for ERBS 11.8) and therefore lower hydrogen.

For common refinery-run fuels, hydrogen content correlates directly with %

aromatics as shown in Figure 2. The ERBS fuels also have a higher density and

a lower heating value per pound than JP5 or JET-A as well as a higher volatility

and end point. The low hydrogen/high aromatics are known to produce high

particle content in flames causing additional smoke and radiant luminosity or heat

flux which creates abnormal increases in operating temperature of the combustor

walls.

No. 2 Diesel has a slightly higher hydrogen content than the ERBS Jet Fuel but

is still lower than JP5. Total aromatics are higher than ERBS 11.8, but

naphthalenes are kept very low due to their adverse effect on Cetane Index.

Naphthalenes have proven to have a more dramatic impact on smoke than

monocyclic aromatics. Diesel fuel also has a higher boiling range, lower thermal

stability, and higher viscosity than JP5 or JET-A. These properties may affect

atomization quality and increase the tendency of the fuel to pyrolize before

burning. This will also increase smoke and carbon deposition.

Motivation

The need for this type of program was created from the worldwide energy crisis

that began in the early 1970s. High quality aircraft fuels have been

traditionally derived from petroleum feed stocks. Limited and dwindling
worldwide reserves of crude petroleum have driven prices up and has placed an

upper limit on availability of certain distillates.

A number of approaches are available to relieve the problem in both the short

and long term.

o Conservation - The most immediate solution is to reduce fuel use. In the

short run, fewer domestic flights and flying with higher load factors make

better use of existing aviation fuel supplies. In the long run, introduction of

growth and new engine designs which are more fuel efficient plus introduction

of airframes with lower drag can make potentially vast improvements in both

usage rates and cost per passenger mile.

In parallel, it is possible to automate flight profiles for minimum fuel

consumption through use of microprocessors.

o Broadening of Aircraft Fuel Specifications - This is a way of increasing the

yield of aircraft quality fuel from a given amount of feedstock. A number of

programs have been underway for the last few years to determine the impact

of wider fuel specifications on aircraft engines and their components,

particularly the combustor.

In general, it has been shown that, when using broad specification fuels, a

potential exists for reduced combustor life, narrower starting envelopes,

increases in smoke and gaseous pollutants, poor thermal stability, and a

greater tendency to foul the fuel handling systems.

o Derivation of Nonpetroleum Fuels - Fuel grade hydrocarbons can be derived

from sources such as shale, tar sand, and coal which are available from huge

deposits in North America. As these resources are exploited, broader fuel

specifications may become necessary especially if the fuel is obtained from coal.

The purpose of this program is to evaluate newer combustor designs in small

engines to minimize or eliminate some of the problems of broadened fuel

specification.

COMBUSTOR DESIGN DESCRIPTION

The baseline combustor for this program is the CT7 combustor used in Naval and

commercial applications. A cross section of this combustor is shown in Figure 3A

and a photograph is shown in Figure 3B. The combustor is a full annular

machined ring design with demonstrated low smoke and 5000 life on JP5 or

JET-A. Predicted smoke characteristics of the T700 combustor from Phase I

analysis are shown in Figure 4. Phase I of this program predicted a 0.2:1 life

ratio reduction on ERBS 11.8 and an increase in smoke number from 28 to 50.

The objective of the new combustors is to achieve metal temperatures and smoke

levels of the baseline combustor with JP5 on ERBS 11.8.
12 PRODUCTION FUEL INJECTORS

PRODUCTION IGNITER

INNER SHROUD

Figure 3A. Baseline T700 Primerless Combustor Cross Section

Figure 3B. Baseline Combustor With Thermocouples Installed
70

0 JP4

se

60

50

40

30

20

10

• JP5 BASELINE (MEASURED)

AERBS JFV (12.8) -\

OERBS 12.3 \ PERCENT H FROM FUEL ANALYSIS

OERBS 11.8 J

OERBS 11.8 (SPECIFICATION MINIMUM)

•ARMY/NAVY REQUIREMENT / ^*V^ > ORIGINAL T700-700

DESIGN AT IRP

•EPA REQUIREMENT

T700/CT7 PRIMERLESS SMOKE FIX COMBUSTOR

SMOKE PREDICTION ON BROAD SPECIFICATION FUELS

AT 0.028 f/a4 (IRP CONDITION)

CONDITION

10 11 12 13 14 15

WEIGHT PERCENT HYDROGEN

Figure 4. T700 Engine Smoke Characteristics Predicted In Phase I

The three new concepts evaluated include the following features:

o Advanced fuel injectors

o Advanced liner cooling techniques

o Combustor airflow redistribution

o Variable geometry swirlers

o Staged combustion (sector burning)

The Concept Approach Matrix (Table 2) shows the application of the features to

the three concept combustors. Cross-sectional views and photographs of the

three concepts are shown in Figures 5A&B, 6A&B, 7A&B and 8A&B.

Concept I Reverse Flow Convection Cooled Combustor (RFCC)

The RFCC combustor cross section is shown in Figure 5A. The combustor is

built around a production T700 combustor incorporating sheet metal spinnings to

form the convection flow paths.

The main spinnings which form the inner and outer convection jackets are welded

to the combustor at one end and interlock between two seal strips at the other

end to form a sliding joint, to relieve thermal expansion. The convection

annulus is partitioned into individual convection circuits for each panel by means

of spun sheet metal dams, which are welded to the combustor shell and slide

against the convection jacket.
TABLE 2

New Concept Approach Matrix

New

Concept Figure Description

5A , 5B Lean Dome

sector burning

if proven necessary) and reverse

flow convection

with impingement

stage

6A, 6B Advanced air7A , 7B blast fuel injection combined with

dilution flow/

impingement

cooled shells

8A, 8B Simulated

variable geometry

swirler with

impingement

cooled replaceable shields

Advanced

Fuel

Injectors

with

Advanced

Cooling

Techniques

X

Airflow

Redistribution

X

Variable

Geometry

Staged

Combustion

X
SLIP JOINT

LEAKAGE ~ 13! W

CUP AIRFLOW

INCREASED

FROM 15% TO

17% OF W.

TYPICAL DILUTION HOLE GROMMET

COOLING

AIR

HOT NOMINAL FLOWPATH

Figure 5A. Reverse Flow Convection Cooled Combustor Cross Section

Figure 5B. Reverse Flow Convection Cooled Combustor (Thimbles Not Installed)
SLIP JOINT

•iEAKAGE~l% W

OUTER IMPINGEMENT SHELL -

IMPINGEMENT COOLING HOLES ONLY

ADVANCED AIR BLAST

FUEL INJECTOR TO

INCREASE CUP AIRFLOW

FROM 15% TO 16% OF W

INCREASED DILUTION AND COOL INC

HOLE DIAMETER TO COMPENSATE

OUTER SHELL A P

SLIP JOINT

LEAKAGE~1%

HOT NOMINAL FLOWPATH

Figure 6A. Dilution Flow Impingement Cooled Combustor Cross Section

Figure 6B. Dilution Flow Impingement Cooled Combustor

10
ADVANCED AIR BLAST FUEL INJECTOR PRODUCTION T700 FUEL INJECTOR

.0750

SWIRL SLOTS

3.1%

AIR HOLES

3.1%

Figure 7A. Advanced Airblast and Production Fuel Injector Cross Sections

v

ADVANCED AIRBLAST FUEL INJECTORS PRODUCTION FUEL INJECTORS

Figure 7B. Advanced Airblast Fuel Injectors and Production Fuel Injectors

11
HIGH AIRFLOW

SWIRLER

GEOMETRY TO

INCREASE CUP

AIRFLOW TO

17% OF W.

STRUCTURAL OUTER SHELL

TYPICAL DILUTION HOLE GROMMET

TIE BARS TO PERMIT DISASSEMBLY

NON STRUCTURAL

SHIELD RINGS

HAST X

HOT NOMINAL FLOUPATH

BOTTOM RING INTEGRAL

WITH INNER SHROUD AFT

FLANGE

Figure 8A. Impingement Cooled Replaceable Shield Combustor Cross Section

Figure 8B. Impingement Cooled Replaceable Shield Combustor

12
The attachment of the dams to the combustor shell requires that all except the

first panel cooling holes be radial drilled instead of axial as on the production

combustor.

Thimbles are used to carry dilution air through the convection annulus. The

thimbles are welded to the jacket and extend through the combustor shell. It

was necessary to limit diametral clearance between the dilution holes and thimbles

to .010 because of trimming considerations. This made it necessary to line drill

all dilution holes through the jackets and shell simultaneously. This line drilling

procedure would probably not be considered feasible for production.

The jackets increase the envelope of the combustor. This was not a problem on

the outer shell but it caused inadequate clearance with the inner flow path (fig.

3A). The inner flow path is a removable shroud which locates the combustor

circumferentially. It also acts as a convection accelerator to help cool the inner

shell, and it serves as a heat shield between the sump on the engine and the

inner shell of the combustor.

The placing of the convection sheath around the combustor makes the latter two

functions of the inner shroud redundant. Since only the aft flange of the inner

shroud is needed to locate the combustor, a shortened inner shroud (Figure 9)

was made. The new piece consisted only of the aft flange with sufficient axial

material to ensure structural integrity.

The aero design presents no significant change from the original concept except

for the deletion of the accelerators from the convection path. These were

considered optional in the proposal and deleted as unnecessary.

SHORTENED INNER SHROUD PRODUCTION INNER SHROUD

Figure 9. Comparison of Shortened Inner Shroud and Standard Inner Shroud

13
Thin shell steady state heat transfer analysis was repeated on all three designs

because there were sufficient deviations from the original Phase I designs to

warrant it. Table 3 shows the results of the analysis.

The lean dome was achieved by using high flowing secondary swirlers. This

puts an additional 2% of WA4 into the primary zone for smoke reduction.

This combustor proved to be the most difficult to build and to trim. Tolerance

control on the sheet metal spinnings proved to be a problem, which was

aggravated by the use of air dams and thimbles. The need to line drill the

thimble holes to minimize leakage would not be practical on a production design.

Concept 2 - Dilution Flow Impingement Cooled Combustor (DFIC)

The combustor cross section is shown in Figure 6A and a photograph is shown in

Figure 6B. The combustor is built around a production T700 combustor. The

impingement jackets are sheet metal spinnings. The spinnings are identical to

those on the RFCC combustor except for different hole patterns. Also, there

are no air dams or thimbles. The seal arrangement for the jackets incorporates

the same sliding joint arrangement as the RFCC combustor, permitting thermal

growth between the jacket and combustor shell.

The combustor as originally designed and analyzed treated each panel as a

separate entity and isolated its impingement flow from the adjacent panels. This

meant that the impingement air for a given panel fed only the cooling and

dilution holes for that panel. This resulted in the first panel receiving the least

amount of impingement cooling and the 3rd panel the most. This combustor did

TABLE 3

Predicted Maximum Metal Temperatures - Three Prototype Combustors

ERBS 11.8 vs Baseline Combustor on Jet A

ERBS 11.8 Jet A

RFCC

End of Panel Mid Panel DFIC ICRS Baseline T700

1st outer

1st inner

2nd outer

2nd inner

3rd outer

3rd inner

1335

1319

1400

1344

1109

1086

1300

1232

1250

1250

1056

1089

1291

1257

1275

1237

1137

1075

1631

1550

1580

1560

1575

1410

1482

1452

1447

1447

1457

1457

14
not totally overcome the fuel effects in the Phase I analysis for this reason. In

the final design, there is a common plenum under the impingement jacket. This

permits an equal number of impingement holes for all panels. Some of the first

panel impingement air eventually goes through the shell at the 2nd and 3rd

panels. All panels now have impingement flows per unit area that are uniform

and provide high levels of cooling.

A thin shell steady state heat transfer analysis of the design was repeated, and

shows that the combustor, on ERBS 11.8 will run 200°F cooler than the baseline

combustor on Jet A. Results are tabulated in Table 3. The prediction was

borne out in testing. (See table 6, page 31.)

A cross section of the Advanced Airblast Fuel Injector is shown in Figure 7A

next to a cross section of a production T700 fuel injector. Photographs of the

two designs are shown in Figure 7B.

The injector employs a central air passage to admit an extra 1% of VVA4 into the

primary zone, and swirl slots in the air shroud to maintain spray stability

margins and to improve the spray pattern. Figure 10 shows the advanced

airblast nozzle spray pattern overlaid on the production nozzle spray pattern.

The advanced nozzle produces a hollow spray with wider overall distribution of

the fuel. This compares to a rich core on the production injector. The

improved fuel distribution, combined with additional air are responsible for the

lower smoke emissions with this nozzle.

PATTERNATOR TEST RESULTS

16

VERIFY A REDUCED FUEL

CONCENTRATION AND

WIDER SPRAY ANGLE FOR

THE IMPROVED AIR BLAST

INJECTOR.

O PRODUCTION T700 INJECTOR

O IMPROVED AIR BLAST

INJECTOR

40 +60

ANGLE

Figure 10. Patternator Results of Advanced Airblast Fuel Injector

15
Of the three combustor designs this one represents the least radical change from

the production design. The same spinnings were used as for the RFCC

combustor; and similar problems were experienced with tolerance control and

fitup of the parts. The absence of thimbles and air dams made these problems

far more manageable, however - to the point where this could be a production

feasible design with a few modifications. The lack of thimbles is considered a

major advantage as it eliminates a large number of small machined parts which

could be misassembled.

Concept 3 - Impingement Cooled Replaceable Shield Combustor (ICRS)

A cross section of the ICRS combustor is shown in Figure 8A and a photograph

is shown in Figure 8B. The ICRS combustor is a simplied version of the

"shingled combustor." The principle is to isolate the structure of the combustor

from direct contact with the flame. The combustor is made from a stack of

structural shell rings with interlocking shield rings. The shield rings have no

pressure drop across them and are allowed to float in the shell rings to relieve

thermal stresses. The design permits replacement of the shield rings by

disassembling the shell rings. To facilitate replacement, the rings are held

together with straps and tackwelds rather than 360° welds as originally

proposed. Thimbles are used to carry dilution air across the two rings and into

the main combustor flow path.

The production internal flow path dimensions were not changed on this

combustor. This means that the outside of the combustor exceeds the production

combustor envelope. This required elimination of the inner shroud. The aft

inner ring of the combustor serves the function of the aft flange of the

production inner shroud. As with the other two designs, the double wall of the

combustor makes the aerodynamic and heat shielding functions of the inner

shroud redundant.

The original concept called for dilution flow impingment cooling of the shingles

similar to concept 2. In practice, this proved a difficult concept to implement as

it required a seal at the aft end of the shingles to regulate cooling air flow.

Coming up with a practical design that could meter cooling air accurately and

accommodate thermal growth of the singles proved impossible within the

constraints of the program. The design was changed to just use the normal

cooling airflow for impingement and to use thimbles for the dilution air. A thin

shell steady state heat transfer analysis of the revised design showed that it

would still produce acceptable temperatures. Results are tabulated in Table 3.

The production CT7 dilution trim was maintained on this combustor except that

preferential cooling was not applied to the impingement cooled areas.

The large number of machined components makes this the most expensive of the

three designs to produce; however, since all parts requiring close fitup are

machined, tolerance control is not a problem. Once all of the parts were

machined, this proved the easiest of the three combustors to assemble. The

high cost is offset by the fact that damaged components can be replaced without

replacing the whole combustor. This advantage is, however, mitigated by the

fact that all three concepts are designed for a 5000 hour service life without

repairs.

16
Another advantage of this design, which was not exploited in this program is

that the shingles can be made out of ceramics or turbine bucket alloys as they

are simple shapes and not load carrying members. This combustor would make a

good vehicle for testing such materials in a future program.

COMPONENT TEST RESULTS AND DISCUSSION

Overview and Summary

The three prototype combustors and the baseline were tested in the T700 heavy

duty test vehicle, a cross section of which is shown in Figure 11. Gaseous

emissions were measured using the GEORGE gas analyzer console (Figure 12),

which is set up to measure HC, CO, CO2 and NOjj.

Two systems were used for measurement of smoke. One was the GE smoke cart

(Figure 13) which uses the ARP1179 smoke spot method to measure smoke. The

other method was by means of a weighed particulate sample taken through the

system shown schematically in Figure 14. In the past, the weighed particulatx

technique has been the preferred method for component rig tests as the results

are more consistent and correlate well with engine test data.

The three prototype combustors were tested on the three broad spec fuels. The

baseline combustor was also tested on JP5, in addition to the other three fuels.

12 ENGINE FUEL

INJECTORS

SMOKE AND

EMISSIONS

PROBES

A.

ENGINE COMBUSTOR

ROTATING EXIT

TEMPERATURE

RAKE

Figure 11. T700 Heavy Duty Test Rig

17
Figure 12. The "George" Gas Analysis System

Figure 13. General Electric Smoke Cart

18
PROBE

\JI—1

 \

COMBUSTOR

FLOWPATH

* J

c

\

HEATEt

.^CABINE

FILTER

HOLDER

•SOLENOID

VALVE

WET TEST

METER

ROTAMETER

FLOW REGULATING

VALVE

EXHAUST

Figure 14. Schematic of Particulate Measurement System

Following the initial screening tests, the relative performance of the three

combustors was evaluated to select the most promising design for final

evaluation. A selection matrix was made (Table 4) and the DFIC combustor was

shown to be the best overall design. This selection was made on the basis of

the following criteria:

o Metal temperature

o Degree of smoke reduction

o Difficulty to manufacture

o Cost to manufacture

o Likelihood of adoption on a production design

The comparison showed the Dilution Flow Impingement Cooled design to be the

most advantageous as it gets the best results in all categories.

This cooling concept is also being used for the LV100 tank engine, a carbon

slurry demonstrator combustor, and is being considered for a low emission CF34

combustor.

Final Parametric Evaluation studied the idle, lean stability, and lightoff

performance, and repeated the smoke measurements. The DFIC combustor was

low on pressure drop in the first phase of the testing (3.2% vs a design 3.85%)

so it was reworked to the design A P for the final parametric phase of the

testing.

19
TABLE 4

Relative Evaluations of Three New Concepts

EhBS 11.8 Max. Difficulty Likelihood

Corrected Metal To Cost to of

Combustor Smoke * Temp Manufacture Manufacture Production

Baseline 55 1654 Production _

Design

DFIC* 36 1233 Least Least Most

Difficult Expensive Likely

RFCC 43 1366 Most Median Least

Difficult Likely

1CKS 44 1486 Median Most Median

Expensive

*Design Selected for Further Evaluation

Profile and Pattern Factor

The combustor pattern factor and profile factors are non dimensional methods of

reporting combustor exit temperatures and temperature distribution. The

temperatures at the exit of the combustor are measured with a double-headed

thermocouple rake. Each rake consists of five thermocouples arranged radially

outward from the inner shell to the outer shell of the combustor. The two rakes

are rotated through three hundred and sixty degrees so that both of the two

five-element thermocouple rakes traverse the entire exit plane of the combustor.

The rake is stepped one hundred times during its traverse of the combustor exit

and takes a total of 1000 temperature measurements.

Profile and pattern factor are then computed for each rake as follows:

Profile factor = Tavg (radial)-Tavg

Tavg-T3

Where T avg (radial) is the average temperature read by an individual

thermocouple at one radial immersion.

Tavg is the average combustor exit temperature from all five thermocouples

Pattern factor = Tmax-Tavg

Tavg-T3

Where Tmax is the highest temperature read by any of the five thermocouples.

Changes in profile factor affect high pressure turbine bucket life while pattern

factor influences high pressure nozzle durability.

20
All three prototype combustors plus the baseline showed a tendency for pattern

factor to increase as hydrogen content decreased. This is attributed to the

tendency of the fuels to form carbon deposits in the swirl cups and disrupt the

normal spray. Pattern factors changed randomly as fuel air ratio was increased.

No trend in any one direction was observed.

The exception to the trend was the #2 Diesel which gave higher pattern factors

than ERBS 12.8. This is attributed to the higher boiling range and lower

thermal stability of Diesel fuel. No fuel effects on profile factor were noted nor

were they expected. There were no observable fuel/air ratio effects on profile

factor.

Profile and pattern factor effects unique to the individual combustors are

discussed below.

o Baseline - Profile/Pattern factor plots for the three fuels and JP5 are

shown in Figure 15. This combustor basically followed the general

trends mentioned above.

FUEL

T700 BASELINE COM3USTOR SERIAL NUMBER 6759

EXIT RADIAL TEMPERATURE PROFILE

MAX TAKEOFF

O DIESEL NO. 2

D ERBS 11.8

A ERBS 12.8

100

A

8Q

t B

Lbl

j

 60

1 C

E

B

D

20

[

0

•

OOJL

 x

X ^

\

\

•

_

.

-

'

t?-o

- ' iToc ^foy

, 1 1

N

^@*^ N / ^ N ^^ \ \ / x

 \ / \ \ /

] \

/ s

'/ 1 /

*y / */'+ • •

/ /' /

/

x

 /

±2o ^ ttoTM

i i i i i

-.3 -.2 -.1 0 ».l +.2

PROFILE MO PEAK TEMPERATURE FACTOR

t.3 -.5

Figure 15. Profile and Pattern Factor, Baseline Combustor (Max Takeoff)

21
o RFCC - Profile and pattern factor results for the three fuels are plotted in

Figure 16. This combustor had the highest pattern factors of all of the

combustors tested. This is attributed partially to changes in dilution jet

trajectories because of the thimbles, and partially to a high pressure drop

(5.0%). The high pressure drop was caused by a missing row of cooling holes

on the first inner panel. The missing cooling holes caused the profile factor

to shift towards a warmer hub and a cooler tip.

o DFIC - This combustor gave the lowest pattern factors of all of the three

combustors. Results are shown in Figure 17. This combustor showed a

tendency to form unstable hot streaks from ERBS fuels - especially at the

cruise conditions. PTF would intermittently jump to 0.39 and then drop to

0.3. This is attributed to carbon deposits forming in the venturi exits and

then falling off. The combustor was operating at 3.2% £ P at this stage of the

program vs 3.85% design AP. When this was corrected in the latter part of

the test program, the unstable hot streak problem was eliminated.

Profile factor was flatter than baseline and was in fact below the -2 sigma

experience level for a production combustor. This is attributed to reduced

overpenetration of the dilution jets resulting in more air being deposited at the

pitchline.

In addition to being tested with the advanced airblast injectors, the combustor

was also tested with production injectors on Diesel Fuel and gasoline. Figure

ISA shows profile and pattern factor results on the #2 Diesel using standard

and advanced fuel injector. The advanced injectors reduce pitchline profile

factor from .045 to .035. The fuel injector related 12th harmonic is reduced by

.015 and is shifted 15° G cup spacing) as shown in Figure 18B. Pattern

factor increased from .26 to .30 going from the standard to the advanced

nozzles, but this is believed to be from a carbon deposit. On ERBS 12.8 PTF

FUEL REVERSE FLOM CONVECTION COOLED

EXIT RACIAL TEMPERATURE PROFILE

O DIESEL NO. 2 MAX TAKEOF F -10X FUE L FLOW

DERBS n.8

AERBS 12.8

100

„

80

s

 B

£

s

S c

B

0.

D

20

E

0

•

<£k x

x

x \

X

\

A

m

•

s

<£'' £

x x. • A •

X \

\

 N

x \

\ N \ A\ \ ) / ,

 \ —

i

1 /! (1 / / -

i I / 1 1 \ ' /> /' / *•

/

 s /

+2o ~2o m

i i , j . _ i

3 -.2 -.1 0 +.1 +.2 +.3 + .4 +.5

PROFILE AKD PEAK TEMPERATURE FACTOR

Figure 16. Profile and Pattern Factor RFCC Combustor (Max Takeoff)

22
DILUTION FLOU IMPINGEMENT COOLED

FUEL EXIT RADIAL TEMPERATURE PROFILE

M A X TAKEOF F

ODIESEI NO. 2

QERBS n.e

AERBS 12.8

IOC

A

8C

i- B

* 60

<

1 c

E

g 40

CL

D

20

E

C

•

x CJ v ^ \

x \

X

\

; *"'*

\ VX

Ti / ")

; ; \" "* / '/ i /

9y / A }' •

'' / /

/ > •

i i i i i

-.1 0 *.l «.2

PROFILE AND PEAK TEMPERATURE FACTOR

Figure 17. Profile and Pattern Factor, DFIC Combustor (Max Takeoff)

DILUTION FLOW IMPINGEMENT COOLED COMBUSTOR

PRODUCTIO N VS . ADVANCE D AIRBLAS T FUEL INJECTOR S

M A X TAKEOF F

NC. 2 DIESE L FUEL

O PRODUCT ION

D ADVANCED AIRBLAST

IOC

A

80

B

1— t

a

*

 60

o

g c

i

S 40

D

20

E

0

•

*£>n x

X

\

\

"

-

/

^ t

*<* D)

±2o t«T

, ,

x • • x \TM \ N \ / c

 / 1

 \ \ ^ \ / 1

»i ] .

x

 •• / / , i /

/ ' /

;»/ /' .xx.

/ / /

/ /' ±2o *2o '

-.3 -.2 -.1 0 +.1 +.2 *.3 +.4 *.5

PROFILE WD PEAK TEHPERATURE FACTOR

Figure ISA. DFIC Combustor, Profile and Pattern Factor, Production Vs Advanced

Airblast Fuel Injectors

23
tlLVTSO N Fio« iKr-ih&ExEK T COOLEC .

:r: .:. «:,;r,:£: AIFFL'S ' FUE L INJECTOR S

MA> THECr r

NC. 2 DIESEL FUEL

ic:

A

s:

I

60

C

4:

?c

E •

O 1 O i

AVC. IQ<

O PRODUCTION

D ADVANCE D A!REL*S T

Kth HAKKOMC

Figure 18B. DFIC Combustor, 12th Harmonic, Production Vs Advanced

Airblast Fuel Injectors

was 0.24. The harmonic shift and lower pitchline profile are attributed to the

hollow spray of the advanced airblast injector versus the solid spray on the

production injector (Figure 10). This results in more fuel being deposited at

the outboard immersions and between cups, and less fuel at the pitchline.

After being reworked to design AP for the final parametric tests, profile

factor shifted towards a warmer hub and a cooler tip. Profile and pattern

factor results for ERBS 12.8 before and after the rework are shown in Figure

19.

Post rework profile and pattern factor results for the fuels are plotted in

Figure 20. Pattern factors on #2 Diesel, ERBS 12.8 and ERBS 11.8 were .26,

.22, and .27 respectively. Pattern factor on this combustor showed the least

sensitivity to fuel effects of any of the configurations including baseline. The

high transient pattern factors observed on the previous test of this combustor

were absent. The increased AP apparently reduces carbon formation in the

swirl cups. Post test inspection showed minimal carbon buildup. The advanced

injector provides a means of minimizing the fuel effect on pattern factor.

o ICRS - Profile and Pattern factors were within production experience. This

combustor showed a stronger tendency than the baseline for increased pattern

factor with decreasing hydrogen. Profile and Pattern factors for the three

fuels are plotted in Figure 21.

24
ERBS 12.8

DILUTION FLOW IMPINGEMENT COOLED

EXIT RADIAL TEMPERATURE PROFILE

MAX. TAKEOFF

D BEFORE MODIFICATION

O AFTER MODIFICATION

100

A

80

t- B

Lkl

_l

5 c

i—

5

g 40

£

D

20

E

0

•

<^D x

x x

X

\

\

.

/

s /

- " ^ Cft

** -2o -To

, ,

N* «X

\

^frl '\ \ ^k

\ \ / ' \

V

 \ /

\ \ / 1

\ / /

^J , / A H /

I 1 7

i . l /

1 1 X

/ / 1 /

5^/ / ••x/

V

 /x /x

x /

/ ^ g :2o TO

i i i i

-.1 0 +.1 ».2

PROFILE AND PEAK TEMPERATURE FACTOR

*.3 •.4

Figure 19. Profile and Pattern Factor Comparison Before and After Modification

FUEL

MODIFIED DILUTION FLOW IMPINGEMENT COOLED

EXIT RADIAL TEMPERATURE PROFILE

TAKEOFF

ODIESEL NO. 2

DERBS 11.8

AERBS 12.8

100

A

80

5

 60

i

i c

£

S 40

E

D

20

E

0

•

>PD s

X

s

&'" Jl

,

A* *

\ \\

^\ / 4";

^r ! ( A * ••

/' / !

ill '

*^ i S

/T / / ^ / / /

' / /

k

 ±2

/

0

 U

 ±2^

i i i i

-.2 -.1 +.1 +.2

PROFILE AND PEAK TEMPERATURE FACTOR

*.4 -.5

Figure 20. Profile and Pattern Factor, Modified DFIC Combustor,

Three Fuels, Max Takeoff

25
IMPINGEMENT COOLED REPLACEABLE SH1NLGE

EXIT RADIAL TEMPERATURE PROFILE

FUEL MAX TAKEOFF - 101 FUEL FLOW

JP-E

ODIESEL NO. 2

D ERBS 11.8

A ERBS 12.8

100

A

80

i- B

*60

3

i

£ 40

£

c

20

c

•

X

\

\

•

-

/

^ /

- f •** yTj '

V A* X • \ \ \

\\ / 1

t; < ?' •

/

 X

B*/7 / /^ • •

/

 x/ x/

x i

-20 i?0

-.2 -.1 0 «.l +.2

PROFILE AND PEAK TEMPERATURE FACTOR

+ .3

Figure 21. Profile and Pattern Factor ICRS Combustor, Max Takeoff

Smoke

Smoke was measured using two methods - the ARP 1179 smoke spot method, and

a weighed particulate sample. The comparisons were made using the particulate

based smoke numbers as the ARP1179 data has historically been unreliable for

component rig tests, due to the effects of high pressure causing condensation of

moisture in the sample lines. The ARP 1179 data will be presented as it is still

necessary to use it where particulate data is not available.

Because the combustors all deviated significantly from the design 3.85% A P, a

correction had to be derived to effect a valid comparison of the three designs.

Figure 22 shows the experience band of cumulative GE smoke experience for all

engines correlated to baffle face fuel air ratio. Smoke numbers were corrected

to the nominal 3.85% AP condition by assuming that the smoke vs fuel/air

relationship followed the same slope as the GE experience bands.

Particulate based smoke number vs % hydrogen is plotted in Figure 23. The

corresponding ARP1179 data is shown in Figure 24.

Raw and corrected smoke data are tabulated in Table 5.

Raw smoke numbers are plotted on the GE smoke experience bands in Figure 25.

ERBS 11.8 and 12.8 both follow a slightly shallower slope than the GE experience

bands. ERBS 11.8 also gave a 55 smoke number vs a predicted value of 50.

The consequence of this is that the ERBS fuels require more leaning out of the

dome than was proposed for this program in order to meet the smoke objective.

26
1

T70C SMOKE RESULTS

CONSISTENT WITH OVERALL EXPERIENCE

50

40

30

20

10

CUMULATIVE G.E. SMOKE

EXPERIENCE ALL ENGINES

0

O T700 BLACKHAWK

D T700 PRIMERLESS COOL TIP

A T700 HIGH FLOW SWIRLER*

A CT7 CERTIFICATION DATA

(THREE TEST AVERAGE)

O NASA BASELINE COMBUSTOR

_l_ JL_ _l_

.11 .12 .13 .14 .15 .16 .17

BAFFLE FACE FUEL/AIR RATIO

.18 .19 .20

*SAME DOME AS RFCC 4

ICRS COMBUSTORS

Figure 22. Smoke Vs Baffle Face Fuel-Air Ratio-Overall GE Experience

60 -

50

40

30

20

10

T700 COMUSTORS

PARTICULATE BASED SMOKE NUMBER

O BASELINE S/N 67S9

O DILUTION FLOW IMPINGEMENT COOLED

A REVERSE FLOM CONVECTION COOLED

?> IMPINGEMENT COOLED REPLACEABLE SHINGLE

11

eo

CM

. t

12 13

HYDROGEN BY HEIGHT PERCENT

•CORRECTED TO 3.91 <

NOMINAL FUEL FLOW

(Correction based on

Figure 22)

14

Figure 23. Particulate Based Smoke Vs % Hydrogen, Four Combustors

27
28

O BASELINE (SMALL BORESCOPE HOLE) S/N 6759

D DILUTION FLOW IMPINGEMENT COOLED

A REVERSE FLOW CONVECTION COOLED

0 IMPINGEMENT COOLED REPLACEABLE SHINGLE

£ 16 -

12 -

8 -

4 -

J

12 13 14

HYDROGEN WEIGHT PERCENT

Figure 24. ARP1179 Smoke, Max Takeoff, Four Combustors

TABLE 5

Tabulated Raw Smoke and Baffle Face Fuel Air Ratio Data

Combustor

Test

S12- Fuel A P* PPS

Baffle

Face

W**

Baffle

Face

w f

PPH

F/A Paniculate

Baffle Based Raw

Face Smoke *

Corrected

Smoke 1

Baseline

DFIC

RFCC

ICRS

Modified DFIC

001

001

003

004

005

006

007

008

009

010

Oil

012

013

014

015

016

JP5

#2 Diesel

ERBS 12.8

ERBS 11.8

ERBS 12.8

ERBS11.8

#2 Diesel

#2 Diesel

ERBS 12.8

ERB 11.8

#2 Diesel

ERBS 12.8

ERBS 11.8

ERBS 11.8

ERBS 12.8

#2 Diesel

85

85

85

85

25

25

3.25

5.0

5.0

5.0

35

35

35

3.85

3.85

3.85

877

559

528

455

6.928

6.841

6.829

6.835

890

898

47

529

7.477

651

432

6.868

17.08

17.08

17.08

17.08

16.61

16.61

16.61

21.60

21.60

21.60

17.80

17.80

17.60

18.00

18.00

18.00

1.175

1.291

1.286

1.274

151

136

134

476

488

1.490

331

341

1.331

377

338

1.236

683

751

750

713

678

676

678

681

680

680

751

757

755

764

778

676

.1614

.1615

.1620

.1555

.1635

.1651

.1659

.1280

.1269

.1267

.1567

.1568

.1575

.1540

.1615

.1519

27.5

42.5

46.5

48

47

43.5

47.5

36

33

50

48

49.

47.8

55

27.5

42.5

46.5

55

36.0

27.5

53.2

43.5

42.5

40.5

41.5

44.2

40

47

= 1.26

"Includes 1/2 of first panel dilution flow

28
CUMULATIVE G.E. SMOKE

EXPERIENCE ALL ENGINES

60-

<:

00

o:

LU

CO

50

DF-2

40 !-

00

o 30

LU

00

CO

£ 20

_i

CJ

i—i

£ 10

DIESEL NO. 2

ERBS 12.8

ERBS 11.8

3.85%AP -

<T> NASA BASELINE COMBUSTOR JP-5

,11 .12

Figure 25.

.13 .14 .15 .16 .17 .18 .19 .20

BAFFLE FACE FUEL-AIR RATIO

NASA Smoke Results Vs Baffle Face Fuel-Air Ratio

Because of its high pressure drop, the RFCC liner ran with a baffle face fuel

air ratio of .128 vs a design objective of .145. Raw smoke numbers on this

combustor met the objectives on the ERBS fuels but smoke was actually worse

than baseline on #2 Diesel fuel. A baffle face fuel air ratio of around 0.128 is

what is actually required to meet the smoke objective on ERBS 11.8.

The DFIC combustor at 3.2% AP indicated sufficient improvement over the

baseline combustor, when smoke numbers were corrected to 3.85% A P» to meet

the objective on all fuels. The Diesel fuel results were of particular importance

here as Diesel fuel is being seriously considered as an alternate fuel for the

T700. This was the only one of the three liners that indicated any improvement

in smoke for Diesel fuel based on initial screening tests. The two lean dome

concepts, in fact, indicated a deterioration in Diesel fuel smoke performance.

For the final parametric evaluation, the AP for the DFIC combustor was

increased by closing off one row of impingement holes on the inner and outer

shells. When the smoke measurements were repeated, the results were

disappointing. There was no reduction in smoke for the ERBS fuels due to

increasing dome A P. The ERBS data fell in on the smoke vs baffle face fuel

air ratio lines from the other combustora. The Diesel fuel data was lost.

ARP1179 data, however, indicated an improvement from the previous Diesel fuel

test of this combustor from 15.3 to 9. Due to the aforementioned problems with

this method on component rig tests we are reluctant to put a number on the

degree of improvement, but we do feel that there was a real improvement in

smoke for Diesel fuel.

29
The smoke data from the three combustors implies the following conclusions:

o There are two different smoke forming mechanisms being observed:

- Droplet burning with smoke being formed by pyrolisis of liquid fuel

droplets and locally rich diffusion buring around the droplet.

- Rich gas phase burning of vaporized fuel

o With Diesel Fuel, the droplet burning mechanism dominates due to its

higher boiling range and lower thermal stability. This is why Diesel

fuel responds more favorably to improved atomization from the advanced

injection than it does to simple leaning out of the dome. The poor

response to the lean dome concept may actually imply a slight

deterioration in atomization from the altered primary/secondary venturi

flow split.

o With ERBS Fuels, the gas phase reactions dominate. This is why the

ERBS fuels respond better to changes in dome stoichiometry than to

improved atomization. All of the dome concepts tested atomize these

fuels to the degree that no further improvement from atomization is

likely. It's possible that optimum atomization on ERBS fuels with the

advanced airblast system was achieved at the 3.2% AP condition and

that at 3.9% /A P the fuel was "overatomized" and burning too close to

the fuel injector tips, with a resultant deterioration in smoke

performance relative to dome stoichiometry.

o The ERBS fuels require more leaning out of the dome than was

originally proposed for this program in order to meet the smoke

objective.

o An "all fuels" combustor, which would operate satisfactorily on ERBS

and Diesel fuels will require a combination of lean dome and advanced

airblast fuel injection.

Metal Temperatures

As expected an increase in metal temperatures was observed with the broad spec

fuels. The highest first panel temperature on the baseline was 1634°F on ERBS

11.8 vs 1380°F on JP5. Although there were no obvious signs of liner distress

after component test, the increase in metal temperature was sufficient to predict

an 0.2:1 reduction in cyclic life.

First panel metal temperatures vs % hydrogen are plotted for all four combustors

in Figure 26. Metal temperatures for all panels are tabulated in Table 6. All of

the combustors ran sufficiently cooler than the baseline combustor to completely

negate the fuel effects; however, the DFIC combustor was the coolest of the

three.

30
MAXIMUM 1ST PANEL METAL TEMPERATURES

M A X TAKEOF F

o

1/1

1700

1600

1500

140°

„< 1300

1200

1100 L

O BASELINE (SHALL BORESCOPE HOLE) S/N 6759

D DILUTION FLOW IMPINGEMENT COOLED

A REVERSE FLOW CONVECTION COOLED

O IMPINGEMENT COOLED REPLACEABLE SHINGLE

OPEN SYMBOL OUTER PANEL

CLOSED SYMBOL INNER PANEL

11 12 13

HYDROGEN BY WEIGHT PERCENT

14

Figure 26. First Panel Metal Temperature Vs Hydrogen, Four Combustors,

Max Takeoff

TABLE 6

Peak Metal Tempertures, of 4 Combustors, 3 Fuels, All Panels

Point S1200B- Cruise

Reverse Flow Dilution Flow

Baseline

Impingement Cooled

Convection Cooled* Impingement Cooled Replaceable Shin gle

~ " ~ ERBS ERBS

Location

Panel 1 Outer

Panel 1 Inner

Panel 2 Outer

Panel 2 Inner

Panel 3 Outer

Panel 3 Inner

Panel 1 Outer

Panel 1 Inner

Panel 2 Outer

Panel 2 Inner

Panel 3 Outer

Panel 3 Inner

ERBS ERBS ERBS ERBS ERBS ERBS

JP-5 DF-2 12.8 11.8 DF-2 12.8 11.8 DF-2 12.8 11.8 DF-2 12.8 11.8

1360

1395

1355

1206

1196

1151

1378

1368

1353

1300

1199

1145

1304

1381

1374

1268

1237

1177

1410

1451

1538

1298

1334

1208

1207

1569

1216

1268

1133

1224

1195

1455

1198

1190

1109

1243

1280

1625

1396

1409

1205

1380

1186

1205

1070

1173

1026

1146

1262

1336

1057

1164

1031

1113

1228

1267

1341

1234

1146

1139

1273

1411

1347

1185

1337

1117

1309

1230

1366

1254

1379

1130

1441

1356

1502

1412

1457

1174

Point S1300B IRP

1380 1380 1409 1349 1313 1248 1248 1151 1243 1183 1384 1389 1486

1363 1511 1466 1634 1576* 1631* 1621* 1191 1235 1254 1220 1307 1345

1374 1462 1491 1448 1277 1309 1350 1219 1164 1210 1399 1408 1518

1241 1336 1323 1321 1296 1336 1395 1195 1178 1239 1171 1190 1191

1211 1255 1276 1246 1166 1203 1206 1116 1082 1104 1422 1403 1539

1163 1178 1207 1198 1256 1353 1379 1126 1118 1149 1306 1127 1182

•First inner panel temperature is high because of manufacturing error and, therefore, not used

for comparison.

31
The first panel of the DFIC Combustor ran 100-150°F cooler on ERBS 11.8 than

the baseline did on JP5. Test results indicate a negative fuel effect; i.e., the

combustor ran cooler as hydrogen decreased. This is probably not real, but the

consequence of the worst hot streaks not always being near a thermocouple. It

does seem reasonable to say that metal temperatures on this combustor are

insensitive to properties of the fuels selected for this study.

Following rework of this combustor to the design pressur drop, metal

temperature measurements were repeated during final parametric testing,

results tabulated in table 7 show are similar to those obtained during the

screening tests.

The

The RFCC combustor ran 100-150°F cooler on ERBS 11.8 than the baseline did on

JP5. This combustor also proved to be insensitive to the fuel properties.

The ICRS combustor duplicated the baseline combustor JP5 metal temperatures

when running on ERBS 11.8. This combustor thus negates adverse fuel effects

on the basis of metal temperature alone. The shingled design provides a further

life improvement by minimizing thermal stresses.

Gaseous Emissions

As the screening points were all at high power, HC and CO gaseous emissions

were very low. Variations were mostly from combustor to combustor with minimal

fuel effect or fuel/air ratio effect.

o HC emissions were too low to measure;

o CO emissions showed no clear cut fuel or fuel/air effect;

o NO., showed a slight tendency to decrease with increasing fuel/air

ratio.

NOY and CO emission results are shown in Figures 27 and 28. CO emissions from

all <3fthe experimental combustors were higher than for the baseline combustors.

The DFIC and RFCC combustors, which had the lowest metal temperatures had

the highest CO levels. The ICRS combustor, which had somewhat higher metal

temperatures than the DFIC and RFCC combustors, was midway between the

baseline and the DFIC and RFCC combustors. The lowered metal temperatures

may be causing increased wall quenching and thus slightly higher CO levels.

TABLE 7

Peak Metal Temperatures, Modified DFIC Combustor

Location

#2D

Cruise

ERBS 12.8 ERB 11.8 #2D

Max Continuous

ERBS 12.8 ERBS 11.8 #2D

Max Takeoff

ERBS 12.8 ERBS 11.8

Panel 1 Outer 1188 1099 1177

Panel 1 Inner 1252 1175 1226

Panel 2 Outer 1228 1138 1094

Panel 2 Inner 1144 1130 1232

Panel 3 Outer 1132 1069 1044

Panel 3 Inner 1171 1172 1138

1231

1204

1167

1234

1118

1180

1324

1188

1268

1258

1166

1193

1160

1158

1150

1258

1163

1172

1185

1238

1193

1202

1150

1231

1261

1086

1286

1277

1118

1183

32
su.

3 ~

§ «

§

UJ

- i

l/l O

14

12

10

11

T700 COMBUSTORS

EMISSION INDEX NOX

TAKEOFF OBASELINE S/N 6759

ODILUTION FLOW IMPINGEMENT COOLED

A REVERSE FLOW CONVECTION COOLED

OIMPINGEMENT COOLED REPLACEABLE SHINGLE

s

1 ,t I

12 13

HYDROGEN BY WEIGHT PERCENT

14

Figure 27. Emission Index NOY Vs Hydrogen, Four Combustors (Takeoff)

8

i

6

a

10

T700 CCXUSTOKS

EMISSION INDEX CO

TAKEOFF

OBASELINF S/K 67S9

DDILUTION FLOW IMPINGENENT COOLED

ADVERSE FLOW CONVECTION COOLED

OIMPINGEMENT COOLED REPLACEABLE SHINGLE

11

t L!

12 13

HYDROGEN BY HEIGHT PERCENT

14

Figure 28. Emission Index CO Vs Hydrogen, Four Combustors (Max Takeoff)

33
During the final parametric testing phase on the DFIC Combustor, the emission

analyzers suffered numerous problems resulting in the loss of some of the data.

NO., analyzer failed during the second half of the ERBS 11.8 test, so NOy data

for^ialf of the ERBS 11.8 testing and the #2 Diesel testing was lost.

Calibration data for the CO analyzer showed inconsistent response, so this data

is only good for rough estimates of relative CO levels.

Gaseous emissions for the final parametric test phase on the DFIC Combustor are

tabulated in Table 8. High power results were essentially a repeat of the

screening test data. Idle HC and CO data indicates idle efficiencies in excess of

98%, consistent with production T700.

Flame Radiation

Flame radiation results are shown plotted in Figure 29 and tabulated in Table 9.

The results show wide variability between combustors, but the same general

trends relative to % hydrogen and fuel/air ratios.

o Radiation increased with decreasing % hydrogen (Figure 29)

o Radiation decreased with increased fuel/air ratio.

The second result was unexpected, but consistent with all four combustors. The

most plausible explanation is that the radiometer is looking through an

incompletely reacted, inhomogeneous mixture. Radiation is being reduced by

unburned carbon particles and pyrolyzing fuel droplets plus the fact that full

adiabatic flame temperature has not been achieved at this point in the combustor.

This effect would become more severe as fuel/air ratio increased thus causing

lower radiation readings. The fact that we are looking at localized

inhomogenities with a narrow angle radiometer would explain the variability

between combustors and the decreasing radiation readings when wall

temperatures would indicate an increase.

The results would indicate that the radiometer geometry should be altered to

view a zone where the reactions are more completely established. Currently we

are viewing the forward most part of the flame front, which is sensitive to

variations in fuel/air ratio as well as part to part variability. Although the

current radiometer configuration is satisfactory for relative comparisons for fuel

effects, the absolute numbers are not reliable.

Overspeed Protection Condition - LBO Performance

The lean blowout fuel flows for the overspeed protection conditions are shown

plotted vs % hydrogen in Figure 30. The DFIC combustor falls short of the

acceptability limit for T700 combustors on ERBS Fuels but gives acceptable results

on #2 Diesel. This may indicate a slight fuel effect on lean blowout performance.

34
TABLE 8

Gaseous Emissions And Idle Efficiency-Dilution Flow Impingement Cooled Combustor

Test

S12014

Fuel

ERBS 12.8

S12015 ERBS 11.8

S12016 *2 Diesel

Point

Cruise

El HC

0

Max Cont. o

Max Takeoff o

Idle 1.464

Cruise

Max Cont. o

Max Takeoff o

Idle NO DATA

Cruise 0

Max Takeoff 0

2.02

El CO

5.96 (est)

El N0>

14.027

12.9

3.92

2.8

8.181 (est) -

CO2*

7.0

3.4

2.5

6.3

6.3

3.2

Idle

Efficiency

99.7

99.6

140

120

t 80

i

20

11.0

T700 COMiUSTORS

TAKEOFF

FLAK RADIATION O BASELINE (SMALL BORESCOPE HOLE) S/N (7S9

D DILUTION FLOW IMPINGEMENT COOLED

6

REVERSE FLOW CONVECTION COOLED

IMPINGEMENT COOLED REPLACEABLE SHINGLE

8

t

8UJ

t

to

UJ

5

, t

Ml

i

0.

•^

t ,

12.0 13.0

HYDROGEN IV MCIO4T PERCENT

14.0

Figure 29 Flame Radiation Vs Hydrogen By Weight Percent,

Four Combustors (Takeoff)

35
TABLE 9

TABULATED RADIATION DATA

Radiation KBTU

Baseline

DFIC

RFCC

ICRS

istor Test Fuel

ne S12001 JP5

S12002 #2Diesel

S12003 ERBS12.8

S12004 ERBS11.8

S12005 ERBS12.8

S12006 ERBS11.8

S12007 #2Diesel

S12008 #2Diesel

S12009 ERBS12.8

S12010 ERBS11.8

S12011 #2Diesel

S12012 ERBS12.8

S12013 ERBS11.8

140

120

100

£ 80

D.

8

*60

UI

=

40

20

n

•

Hr

Cruise

-10%

wf

33

68

74

87

105

41

67

88

95

112

Ok.

Ftz

Max Takeoff

Nominal +10% -10% Nominal +10%

wf

26

64

63

59

84

95

76

43

36

76

76

89

99

^w*

Wf

24.5

50

53

68

68

100

70

43

40

64

80

89

79

wf

42

43

80

84

92

125

68

45

41

67

115

130

138

wf

34

73

90

115

130

84

43

46

54

87

110

115

wf

32

79

127

88

45 4

48

68

64

98

98

T700 ACCEPTABILITY LIMIT

-

00

r- 1

1/1

&UI

t .

CO

es*.

t— i

1/1

sUI

\

CM

t

u.

0

J

*NO BLOWOUT OCCURRED WITH #2 DIESEL

11 12 13 14

HYDROGEN BY WEIGHT PERCENT

Figure 30. Lean Blowout Fuel-Air Ratio Vs Hydrogen By Weight Percent

36
Lightoff/LBO Performance

Figure 31 shows lightoff fuel flow vs 6 (Longwell parameter). Sea level lightoff

is acceptable for all fuels although lightoff fuel/air ratios on ERBS 11.8 and #2

Diesel were higher than for ERBS 12.8. Altitude lightoff shows a deterioration

from production T700 levels in that 20000 ft altitude lightoff is marginal with

poor propagation between cups vs a reliable lightoff for production T700.

Lightoff data is tabulated in Table 10. ERBS 11.8 altitude lightoff was not

achieved due to power supply problems in the ignition system.

.50 -

.30 -

.20

5 -10

5.05

.02

k 20,000 FT

ALTITUDE

LIGHTOFF

%

JP-5 DATA BAN

DILUTION FLOW IMPINGEMENT COOLED

+ ERBS 12.8

k ERBS 11.8

t DIESEL NO.2

SEA LEVEL

LIGHTOFF

PREPONDERANCE OF DATA

T700 DATA BAND

25 50 100 200 400

LONGWELL STABILITY PARAMETER, (atm.)1'

8 °R ft3 sec./lbs

Figure 31. Modified DFIC Combustor, Advanced Airblast Fuel Injectors,

Lightoff Performance

37
W3 W4

Fuel I'l'S PPS

Combuslur

TABLE 10

Tabulated Lightoff Data

IN HUA

L/O

PPH

Wf

LBO

PPH

Time

lo

Li^ht

See

f / A I/ A

blillli luci

l.jghtoft

I.HBS 12.8

tKBs 11.8

I2D

EKBS 12.8

ERBS 11.8

EhBS 12.8

ERBS 11.8

»2D

1

ATM1

1.27

1.19

1.11

.56

NO Light

2.79

2.53

2.81

ft 1 •" °K rr

.'J64 51.B- J

.922 50. b

.8b 50.9

.434 24

on EKBS 11.8 Dut

.49b 23

2.16 114

1.96 115

2.18 115

55K 40

55J 50

5JO 44

20.0UO

544 51

533 62

Idle

869 115

870 80

869 110

38 112.

47 113.

39 119.

Ft Lighloff

45 62.1

ii> t >\ v HroL)lcnia

65 49. 3

Lighlolf

70 329

76 369

53 332

Ib/sec

V

oon,bustor ' -

074

1

2

32

.0113

.015

-OH

.033

.035

.0147

.0113

.0140

.01.2

.083

.070

.181

.19:

.0785

.062

.0766

Idle Efficiency

Idle efficiency was greater than 98% for all fuels, which is in the range of

production T700. No fuel effect was noted for idle efficiency.

38
OVERALL RESULTS

The two primary objectives of this program were controlling metal temperatures and

smoke with low hydrogen fuels.

All three combustors reduced metal temperatures sufficiently to negate any life

reduction from low hydrogen fuels. The Dilution Flow Impingement Cooling

concept was chosen because it provides the lowest metal temperatures with the

least amount of complication. The shingled combustor concept is still promising

for its ability to use materials such as ceramics for the shingles. The

disassembly feature would make this a good vehicle for evaluating such materials

as a future program.

Smoke reduction fell short of objectives although the 5% A P on the RFCC

combustor enabled us to determine what was necessary to achieve those objectives.

Additional leaning out of the dome is necessary to meet the objective on ERBS

fuels but the advanced airblast injection appears necessary for Diesel fuel. A

combination of high flowing swirlers and advanced airblast injectors appears

necessary for a combustor that will operate satisfactorily on all three fuels. Part

of the additional airflow can be achieved by further modification to the fuel

nozzle.

These designs showed slight deterioration of lightoff and lean blowout

performance margin. Further smoke reductions will aggravate this problem.

Some of GE's large commercial engines use locally rich cups over the igniters to

offset this. This is preferred over sector burning or variable geometry for the

degree of enrichment required.

Based on the results of this program, the following concepts show the most

promise for a combustor that would handle ERBS fuels and #2 Diesel fuel:

o Advanced Airblast fuel injection with a lean dome for smoke control on

ERBS fuels and Diesel fuels.

o Dilution Flow Impingement Cooling the combustor liner to achieve 5000

hour life on all fuels.

39