The use of broad specification fuels in aircraft turbine engine combustion systems was examined. Three different combustor design concepts were evaluated for their ability to use broad specification fuels while meeting several specific emissions, performance, and durability goals. These combustor concepts covered a range from those having limited complexity and relatively low technical risk to those having high potential for achieving all of the program goals at the expense of increased technical risk

Dodds, W. J.

English

NASA Technical Reports Server

NASA/GENERAL ELECTRIC BROAD-SPECIFICATION FUELS 
COMBUSTION TECHNOIDGY PROGRAM - WASE I 
Willard J. Dodds 
General Electric 
Aircraf t  Engine Group 
The use of broad-specification fue l s  i n  a i r c r a f t  turbine engine combus- 
t ion systems presents several  design problems. 
pol lutant  emissions increase and the combustor performance and durabi l i ty  
requirements become more d i f f i c u l t  t o  meet as the fue l  specif icat ions are 
relaxed. .  Fuel hydrogen content w i l l  be lower than i n  presently used fue ls ,  
causing increased v i s i b l e  smoke output, increased carbon deposition on fue l  
nozzles and combustor l i ne r s ,  increased NOx %emissions, and increased flame 
luminosity, resu l t ing  i n  increased rad ian t  heat t ransfer  and shorter  l i f e .  
Fuel v o l a t i l i t y  w i l l  be lower and v iscos i ty  w i l l  be higher than i n  presently 
used fue l s .  This w i l l  r e s u l t  i n  more d i f f i c u l t  cold s tar t  and alt i tude 
r e l i g h t  and greater d i f f i c u l t y  i n  achieving sa t i s fac tory  emissions leve ls  a t  
low power conditions.  Thermal s t a b i l i t y  may be poorer than i n  presently used 
fue ls ,  causing fue l  system deposits and fue l  i n j ec to r  plugging. 
I n  general, l eve ls  of exhaust 
Design approaches t o  counteract the e f f e c t s  of decreased fue l  hydrogen 
content include the use of sho r t  combustors with improved l i n e r  cooling tech- 
niques. Improved combustor dome and swir ler  designs eliminate carbon deposi- 
t ion  and improve primary zone mixing, thereby decreasing smoke formation and 
flame luminosity and minimizing r epe t i t i ve  hot streaks which can reduce l i n e r  
l i f e .  I n  advanced designs, smoke, NOx and flame luminosity can a l l  be reduced 
by providing fo r  lean combustion a t  high power operating conditions. Effects  
of increased viscosi ty  and reduced v o l a t i l i t y  can be reduced by the use of 
improved dome, fue l  in jec tor  and s w i r l e r  designs t o  improve fue l  atomization 
and mixing a t  l igh tof f  and low power operating conditions, and by providing 
low ve loc i t ies  and near-stoichiometric mixtures i n  the combustor primary zone 
a t  low power operating conditions.  Fuel thermal s t a b i l i t y  e f f e c t s  can be 
reduced by reducing fue l  manifold temperatures and by using more e f fec t ive  
thermal insulat ion i n  fue l  sys  t e m  components. 
I n  Phase I of the NASMGeneral Electric Broad-Specification Fuels Tech- 
nology program, three d i f f e r e n t  combus tor  design concepts w i l l  be evaluated 
fo r  t he i r  a b i l i t y  t o  use broad-specification fue l s  while meeting several  
spec i f ic  emissions, performance, and durabi l i ty  goals .  These combustor con- 
cepts  cover a range from those having l i m i t e d  complexity and r e l a t ive ly  l o w  
technical r i s k  to  those having high poten t ia l  f o r  achieving a l l  of the program 
goals a t  the expense of increased technical r i sk .  
The concept with the least complexity is the basic CF6-80 combustor. Th'is 
advanced single-annular combustor i s  a direct der ivat ive of the successful 
CF6-50 combustor design. Compared to the CF6-50 design, the CF6-80 combustor 
109 
https://ntrs.nasa.gov/search.jsp?R=19800020815 2020-03-21T03:28:56+00:00Z
l ength  has been reduced by 8 cm,  counter ro ta t ing  dome swirlers a re  used r a t h e r  
than the co ro ta t ing  design, and the l i n e r  f i l m  cool ing s lots  a r e  a newly 
developed ro l l ed - r ing  design t h a t  f e a t u r e s  improved f i l m  cool ing e f f ec t iveness  
8nd maximum r e s i s t a n c e  t o  f i l m  s lo t  c losu re .  
The second concept i s  a para l le l - s taged  double-annular design s i m i l a r  t o  
t h a t  used i n  the NASUGE Experimental Clean Combustor and E3 programs. 
l i g h t o f f  and l o w  power opera t ing  condi t ions ,  a l l  of  the  f u e l  is burned i n  the 
p i l o t  s tage  , which is designed t o  provide l o w  ve loc i ty ,  near-s toichiome t r i c  
primary combustion. A t  high power condi t ions ,  both the p i l o t  and main s t ages  
are fueled,  bu t  m o s t  of the f u e l  is i n j e c t e h  i n t o  the main s t age  dome. 
dome is  designed t o  provide l ean  combustion and s h o r t  res idence t i m e s  t o  reduce 
NOx and smoke formation, thereby reducing flame luminosity e f f e c t s .  
A t  
This  
The t h i r d  concept i s  an advanced, s h o r t  s ingle-annular  combustor which 
employs va r i ab le  geometry s w i r l e r s  t o  provide optimum flow rates and s to i ch io -  
metr ies  i n  the dome reg ion  a t  the var ious  operat ing condi t ions .  A t  l i g h t o f f  
and low power condi t ions ,  the swirlers a re  closed down t o  reduce the combustor 
ve loc i ty  t o  provide near-s toichiometr ic  pr.imary zone mixtures .  A t  h igh power 
condi t ions,  the  s w i r l e r s  a r e  opened to provide lean ,  high ve loc i ty  combustion. 
The combustor tes t  program w i l l  c o n s i s t  of screening t e s t s  of a base l ine  
conf igura t ion  and approximately f i v e  modif icat ions of each combustor concept .  
About s i x  add i t iona l  refinement tests w i l l  then be conducted t o  improve the 
performance of s e l ec t ed  combustor conf igura t ions  and to  more completely docu- 
ment combustor operat ing c h a r a c t e r i s t i c s  and f u e l  p rope r t i e s  e f f e c t s .  A l l  
t e s t i n g  w i l l  be conducted using a f u l l - s c a l e  CF6-80 s e c t o r  tes t  r i g  which i s  
designed t o  opera te  a t  the f u l l  sea- level- takeoff  pressure and temperature 
condi t ions  of the  CF6-80 engine.  
110 
Combustor Design Considerations 
Fuel Property Change 
Reduced Hydrogen 
Content/Higher 
Aromatics 
Increased Viscosity/ 
Reduced Voiatillty 
* Reduced Thermal 
Stability 
Problems 
* increased Flame 
Luminosity (Increased 
Liner Temperatures) 
* Increased Smoke 
* increased NOx 
* increased Carboning 
* increased Ground 
Start/Reiight Difficulty 
* increased Low Power 
Emissions (CO &HC) 
* Fuel Valve & Nozzle 
Fouling 
Approach 
Lean-Well Mixed 
Combustion at High 
Power 
* Short Combustor- 
Reduced Liner 
Cooling Requirements 
* improved Dome/Swlrler 
Rich-Low Velocity 
improved Dome/Swirler 
Increase Fuel System 
Designs 
Combustion at Low 
Power 
Designs 
insulation 
Baseline CF6-80 Combustor 
Short Single Annular Combustor Design 
Counterrotating Dome Swirlers 
* Advanced Liner Cooling Slot Design 
* Short Prediffuser 
111 
Short 
Double Annular Combustor 
Double Annular Combustor Design 
Low Velocity Pllot Stage - Near Stoichiometric Primary Zone 
High Velocity Main Stage - Lean Primary Zone Combustion at High Power 
0 Cenbrbody Dilution for improved Mixing 
0 Utilizes NASNGE ES Swirier Componenis 
Combustion at idle 
Variable Geometry Combustor 
+ 
-- 
a Very Short Single Annular 
0 Dome Swlrier Closed for Low Power Operation - Low Velocity - Rich Primary Zone Combustion - Increased Pressure Drop 
- High Velocity - Lean Primary Zone Combustion - Short Residence Tlme 
o Dome Swlrier Open for High Power Operation 
112 
Combustor Design Parameters 
B8.ellne Double Varlable 
CF6-SO Annular Geometry - Plol- - Main 
Low Power (Idle) 
Dome Reference Velocity , m/s 8.3 6.6 - 5.7 
1 .o 
Dome Swirler Equivalence 
Ratlo 0.73 1.1 - 
High Power (Takeoff) 
Dome Reference Velocity, 
Dome Overall Equlvalence 
m/s 11.3 9.0 28.8 19.3 
Ratio 0.88 0.63 0.63 0.60 
Combustor Length, cm 27.7 221 22.1 20.8 
Planned Test Program 
Scope: Screening Tests on Six Configurations of Each 
Concept (18 Tests Total). 60 Percent of Engine 
Pressure. 
* Refinement Tests on Two Most Promising 
Concepts (6 Tests Total). Some Tests at 
Full Engine Pressure. 
Test 
Vehicle: CF6-80 Hlgh Pressure (Up to 3.5 MPa) Five 
Cup (60-Degree) Sector Combustor Test Rig. 
Test 
Facility: Test Cell A3 - Evendale. 
113 


NASA/General Electric broad-specification fuels combustion technology program, phase 1

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server