The effect of antimisting kerosene (AMK) flow characteristics on fan jet engines and the impact of degradation requirements on the fuel system was evaluated. It was determined from the present program that AMK fuel cannot be used without predegradation, although some degradation occurs throughout the fuel feed system, expecially in the fuel pumps. There is a tendency toward FM-9 AMK additive agglomeration and gel formation when the liquid flows at a critical velocity through very small passages. The data indicate this phenomenon to be a function of the degree of degradation, the passage size, the differential pressure, the fluid temperature, and the accumulated flow time. Additionally, test results indicate that the long term cumulative effects of this phenomenon may require more degradation than the theoretical requirement determined from short term tests

Schmidt, H. W.

English

NASA Technical Reports Server

THE USE OF ANTIMISTING KEROSE!iE (AMK) I N  TURBOJET ENGINES 
Haro ld  W. Schmidt 
NASA Lewis Research Center 
SUMMARY 
Tes t  conducted by t h e  FAA have demonstrated t h e  c r a s h - f i r e  r e s i s t a n c e  of 
a n t i m i s t i n g  kerosene (AMK), a j e t  f u e l  c o n t a i n i n g  an a n t i m i s t i n g  a d d i t i v e .  
T h i s  a d d i t i v e ,  a high-molecular-weight polymer, causes t h e  f u e l  t o  r e s i s t  
a tomiza t i on  and 1 i q u i d  shear fo rces ,  which a l s o  a f f e c t  f l o w  c h a r a c t e r i s t i c s  i n  
t h e  engine f u e l  system. 
the  pressure d i f f e r e n t i a l  as i n  t h e  case o f  Newtonian l i q u i d s .  However, t h i s  
shear r e s i s t a n c e  and i t s  r e s u l t a n t  non-Newtonian f l o w  c h a r a c t e r i s t i c s  can be 
negated by molecu la r  shear degradat ion.  
eva lua te  t h e  e f f e c t  o f  AMK f l o w  c h a r a c t e r i s i t c s  on f a n - j e t  engines and t h e  
impact o f  degradat ion  requirements on t h e  f u e l  system. 
The f l o w  r a t e  o f  AMK i s  n o t  a cons tan t  f u n c t i o n  o f  
The purpose o f  t h i s  program was t o  
I t  nas been determined f r o m  t h e  present  program t h a t  AMK f u e l  cannot be 
used w i t h o u t  predegradat ion,  a l though some degradat ion  occurs throughout t h e  
f u e l  f eed  system, e s p e c i a l l y  i n  t h e  f u e l  pumps. 
b i l i t y  o f  a mechanical f u e l  degradat ion  system has been demonstrated, t h e  
p r a c t i c a b i l i t y  and c o s t  e f fec t i veness  must be es tab l i shed .  
problem areas have been i a e n t i f i e d .  
Al though t h e  t e c h n i c a l  f e a s i -  
Several  p o t e n t i a l  
There i s  a tendency toward FM-9 AMK a d d i t i v e  agglomerat ion ana g e l  f o r -  
mat ion  when t h e  l i q u i d  f lows a t  a c r i t i c a l  v e l o c i t y  th rough ve ry  smal l  pas- 
sages. The d a t a  i n d i c a t e  t h i s  phenomenon t o  be a f u n c t i o n  o f  t h e  degree o f  
degradat ion,  t h e  passage s i ze ,  t h e  d i f f e r e n t i a l  pressure, t h e  f l u i d  tempera- 
tu re ,  and t h e  accumulated f l o w  t ime. A d d i t i o n a l l y ,  t e s t  r e s u l t s  i n d i c a t e  t h a t  
t he  long- te rm cumula t ive  e f fec ts  of t h i s  phenomenon may r e q u i r e  more degrada- 
t i o n  than  t h e  t h e o r e t i c a l  requirement determined from shor t - te rm t e s t s .  
INTRODUCTION 
A n t i m i s i t i n g  kerosene i s  a ke rosene- f rac t i on  j e t  f u e l  c o n t a i n i n g  an addi- 
t i v e  which reduces t n e  f l a m m i b i l i t y  o f  t h e  f u e l  i n  an a i r c r a f t  crash. The 
most p romis ing  AMK a d d i t i v e s  are  high-molecular-weight polymers t h a t  are d i s -  
so lved i n  J e t  A f u e l  i n  concen t ra t i ons  i n  the  range o f  0.3 percent .  These 
a d d i t i v e s  have demonstrated t h e i r  a b i l i t y  t o  i n h i b i t  i g n i t i o n  and f lame propa- 
g a t i o n  o f  t h e  re leased  f u e l  i n  s imu la ted  crash t e s t s .  
The AMK f u e l  r e s i s t s  m i s t i n g  and a tomiza t i on  f r o m  wind shear and impact 
T h i s  agglomerat ion s i g n i f i c a n t l y  fo rces  and i n s t e a d  tends  t o  fo rm globules.  
reduces i g n i t i b i l i t y  and f lame propagat ion.  
499 
https://ntrs.nasa.gov/search.jsp?R=19810010537 2020-03-21T09:03:04+00:00Z
The a n t  imi st i ng additive ( FM-9) selected f o r  more comprehens i ve t e s t i  ng 
in  t h i s  program was developed by the Imperial Chemical Industries and the 
Royal Aircraft Establishment ( R A E )  of the United Kingdom and i s  being eval- 
uated f o r  crash-fire resistance by the FAA and RAE. 
The properties of AMK that  make i t  f i r e  res i s tan t  also give i t  un- 
desirable flow character is t ics  in the engine fuel feed system. The main prob-  
lems are i t s  non-Newtonian flow character is t ic ,  which resul ts  in lower f r ic -  
t ion losses a t  low flow rates;  a variable onset of turbulent flow rates ,  wnich 
depend on the degree of degradation; and the tendency f o r  the additive t o  
agglomerate with gel formation when the liquid i s  throt t led (accelerated) 
t h r o u g h  small clearances o r  passages. 
In  cooperation with the FAA,  NASA conducted a program t o  evaluate AMK f o r  
a i r l i n e  use through a contract the P r a t t  & Whitney Aircraft Group who  tested 
a n d  evaluated the e f fec ts  of FM-9 AMK on the fuel feed system of the JT8D 
engine. The purpose of tne t e s t s  was t o  identify operating problems, assess 
the adaptabili ty of existing engines t o  AMK, and t o  determined the potential 
v iab i l i ty  of t h i s  fuel in present and future fan-jet engines. The data pre- 
sented herein were obtained i n  t h a t  program. 
Cri t ical  fuel system components and subsystems were tested and evaluated 
f o r  AMK compatibility. 
control ler ,  system f i l t e r s ,  nozzles, and combustors. 
Components tes tea  included the fuel pump, the fuel 
The program included laboratory t e s t s  f o r  fuel  characterization, chemical 
compabi l i t y ,  thermal stabi 1 i t y ,  heat t ransfer ,  and rheological properties. 
System t e s t s  included nozzle spray-pattern t e s t s ,  f i l t r a t i o n  l imits ,  con- 
t r o l l e r  function, pump performance, ignition s t a r t ,  a n d  re l ight  t e s t s .  
AMK CHARACTERIST ICs 
Antimisting kerosene fuel exhibits the greatest  shear resistance and 
crash-fire resistance before exposure t o  snear, such a s  pumping flow t h r o u g h  
pipes and f i t t i n g s ,  f i l t e r s ,  or other components. 
of these shear forces tends t o  break the polymeric molecules, thereby reducing 
the average molecular- weight and  the subsequent shear resistance. Continua- 
t ion of such shear degradation causes AMK t o  revert t o  the original properties 
of the base fuel.  
Successive exposure t o  any 
This character is t ic  provides the possibi l i ty  of using AMI( .in existing 
engines i f  the level of degradation required f o r  acceptable performance for  
each c r i t i c a l  component i s  assured. 
The AMK additives have a molecular weight of over 5 000 000, and  these 
molecules tend t o  r e s i s t  the turbulent flow in liquid boundary layers and 
extend the viscous flow regime, thereby acting as a drag reducer. 
ance t o  shear and droplet breakup also affects  nozzle performance. 
ple, f igure i ( a )  shows the typical atomization of Je t  A fuel  in a standard 
JT8D nozzle a t  ignition flow rates. Figure l ( b )  shows the behavior of uw- 
The res i s t -  
For  exam- 
500 
degraded AMK in the same nozzle. 
the standard nozzle, and f igures  3 and 4 for  nozzles with successively in- 
creased atomization capabi l i t i es  bu i l t  into the i r  designs. 
ure 5,  the calibration curve fo r  turbine flowmeters with antimisting fuel does 
not exhibit  constant K (cycle per cubic meter); therefore, the flowmeter must 
be recal ibrated for  any given conditions (degradation level and temperature) to  
be used. 
Similarly, f igure 2 shows fuel behavior fo r  
As snown in f ig-  
With the use of a micromotion mass meter, the flow ra te  of AMK can be 
accurately measured a t  any level of degradation ( f i g .  6 ) .  
tha t ,  a t  the level of degradation required by the propulsion system, the nor- 
mal accuracy of turbine flowmeters i s  obtained. 
I t  was determined 
Heat-transfer measurements show a marked reduction in the heat t ransfer  
Note t h a t  
with undegraded AMK in the turbulent flow range, because of the boundary-layer 
turbulence suppression of the undegraded FM-9 molecules ( f i g .  7 ) .  
increasing levels of degradation causes the heat-transfer coefficient t o  
approach Je t  A values. The thermal s t a b i i i t y  of AMK ( tab le  I )  was better than 
Je t  A ,  and fur ther  s t u d y  i s  planned t o  determine the reason f o r  t h i s  apparent 
improvement. 
Two additional character is t ics  were tested: water so lubi l i ty  and  mate- 
The resul ts  of the water so lubi l i ty  t e s t s  are shown in 
The s t a n d a r d  t e s t  
r i a l s  compatibility. 
table 11. Although the urisheared Je t  A/FM-9 appears t o  absorb less  water t h a n  
the Je t  A fue l ,  fur ther  investigation i s  required because some of the FM-9 
additive separated from the solution during the t e s t s .  
procedure used f o r  t h i s  t e s t  may not be representative of the actual AMK/water 
compatibility, b u t  t h i s  will  have t o  be thoroughly explored. 
Some incompatibi 1 i t i e s  of component materials were observed and  measured 
witn the FM-9 AMK tes ted.  The hardness a n d  t ens i l e  strength of Buna-N and 
fluoro-silicone elastomers were lowered af te r  a 30-day exposure, a n d  there was 
a tendency towards swelling. Also, chemical interaction was measured in 
a l l o y s  containing copper, although bronze materials in the t e s t  components 
were n o t  adversely effected by the AMK during the t e s t  program. 
FUEL SYSTEM COMPONENTS TESTS WITH FM-9 AMK 
The non-Newtonian flow behavior, caused by these 'large FPi9 molecules, i s  
more pronounced in flow through small passages or close clearances (such a s  
t h r o u g h  f i l t e r s  and  fuel  flow control lers) .  The flow velocity of AMK t h r o u g h  
a capi l lary o r  f i l t e r  increases ( i n  Newtonian fashion) as a function of  pres- 
sure unt i l  a "c r i t i ca l "  t ransi t ion occurs, requiring a sharply increased r a t e  
of pressure increase t o  cause a continuing flow-rate increase ( f ig .  8 ) .  Dur- 
ing t h i s  t ransi t ion,  the AMK molecules have an increased tendency t o  agglom- 
erate ,  forming a gel precipitate.  (This "cr i t ica l  region i s  also a function 
of the degree of degradation.) 
501 
These c r i t i c a l  velocity e f fec ts  can be controlled o r  accommodated in sev- 
eral  ways: 
(1) By increasing the level of degradation 
( 2 )  By increasing the flow area.of f i l t e r s  
(3)  By increasing the flow passage length t o  diameter ra t io ,  thereby 
reducing the flow-rate increase f o r  a given cnange in pressure 
( 4 )  By increasing the temperature, which increases the velocity a t  whicn 
c r i t i c a l  flow occurs 
As the pressure and flow r a t e  i s  increased past the c r i t i c a l  velocity, a sec- 
ond c r i t i ca l  velocity i s  reached when the shear forces are suf f ic ien t  f o r  
molecular fragmentation and AMK degradation. 
gradation process: 
Two parameters e f fec t  the de- 
(1) Time of exposure t o  degradation process 
( 2 )  The amount of s t r e s s  o r  energy a t  or above degradation s t r e s s  levels 
The use of AMK fo r  crash-fire mitigation requires the fuel i n  the air- 
c r a f t  fuel tanks t o  be maintained in a re la t ively undegraded s t a t e ,  and ,  as 
the fuel  i s  metered t o  the engine, a degradation level, as required t o  permit 
the AMK flow t h r o u g h  a l l  c r i t i c a l  components, must be provided. 
require an energy e f f i c i en t  degrader t h a t  can provide the hignest molecular 
shear s t r e s s  with the lowest possible power requirement. 
This will 
The major problem in the e f for t  t o  evaluate the e f fec ts  of AMK on the 
performance of fuel system components was the accurate measurement of tne 
degree o r  percent of degradation of the t e s t  fuel .  
of ANK versus Je t  A proviaed the best discrimination of the viscosity change 
as a function of the degree of shear degradation of three viscosity measure- 
ment techniques used ( f i g .  9 ) .  
The f i l t r a t i o n  ra te  r a t i o  
Seventeen-micrometer mesh metal f i l t e r s  were used as t h e  measurement 
standard, which gave a good discrimination of degradation as a function of 
s t r e s s  time t o  a f i l t r a t i o n  r a t e  r a t io  (AMK/Jet A )  of approximately 4; b u t  
below 4 the curve f l a t t ens  o u t .  However, by measuring the amount of flow as a 
function of shear exposure and using 8- and 10-micrometer f i l t e r s ,  better vis- 
cosi ty  discrimination was achieved a t  the higher degradation levels. 
The JT8D fuel  pump assembly was used t o  aegrade the AMK t e s t  fuel  t o  de- 
s i red levels. 
number o f  passes through the pump. 
Figure 10 shows the degradation achieved as a function of the 
The difference in the power input into the pump was n o t  measurable, even 
t h o u g h  significant degradation was achieved in the process. Preliminary data 
tend t o  support the poss ib i l i ty  t h a t  the drag reduction character is t ic  of the  
polymer additive in par t  compensates fo r  the energy used in the degradation 
process. 
t ion  energy requirement and  t o  identify the best method of degrading the fue l .  
Follow-on experimental t e s t s  are expected t o  quantify the degrada- 
Qual i ta t ive  comparisons of the emissions chdracter is t ics  of AMK versus 
Je t  A using the standard nozzle and  the l a t e r  low-emissions nozzle are shown 
502 
in figure 11. 
passes through the fuel  pump) i s  only par t ia l ly  degraded, and i t  i s  expected 
that AMK degraded t o  f u l l  system requirements will  meet Jet  A emission values. 
Subsequent tes t ing will  determine the optimum level of degradation. 
character is t ics  of AMK and J e t  A.  
mately 25 percent higher fuel flows t o  achieve f u l l  ignition in the nine-can 
burner t e s t  r i g  ( f i g .  1 2 ) .  
AMK t o  be equivalent t o  Jet  A. 
I t  should be pointed o u t  that  3-pass AMK ( i . e . ,  AMK a f t e r  3 
Tests were conducted t o  compare engine-ignition and al t i tude-rel ight  
Par t ia l ly  degraded AMK required approxi- 
Further t e s t s  are expected t o  show fu l ly  degraded 
The a l t i tude  rel ight  t e s t s  a t  an a i r  flow of 2.27 kilograms were the same 
Performance tes t ing of the fuel controller with 16-pass AMK was completed 
A n  8-hour closed-loop cycle t e s t  was subsequently completea w i t h o u t  
f o r  AMK and  Je t  A ;  a t  a l l  other flow rates ,  the AMK re l ights  were poorer. 
without detrimental e f fec ts  in comparative performance between Jet  A and 16- 
pass AMK. 
measurable differences o r  e f fec ts  from the AMK. 
Pump tes t ing and calibration with undegraded AMK snowed no detrimental 
effects .  
for  a given speed was observed with par t ia l ly  degraded and undegraded fuel .  
This drag  reduction influence became negligible w i t h  increasing degradation, and 
pump performance w i t h  16-pass AMK was the same as for  J e t  A fuel .  
An apparent improvement in the flow ra te  and  different ia l  pressure 
RESULTS A N D  CONCLUSIONS 
1. I t  i s  technically feasible  t o  operate JT8D engines with 0.3 percent 
FM-9 AMK fuel.  
2. The degree of degradation t h a t  i s  necessary for  AMK fuel compatibility 
w i t h  existing fuel system designs has  been determined t o  be in the f i l t e r .  
r a t io  range of 1 .2 ,  o r  lower, using a 17-micrometer f i l t e r .  
3. The primary modificatim requirements f o r  turbofan j e t  engines t o  
accommodate FM-9 AMK will  be the addition of a fuel degrader before the fuel  
pump, which will provide the selected level of degradation. 
4. Methods of predegrading AMK fuel in a f l i gh t  cer t i f ied  system must be 
evaluated fo r  pract icabi l i ty ,  cost ,  and energy effectiveness. 
5. Data obtained with JT8D engine are applicable t o  other engines because 
the character is t ic  limiting parameters of AMK are the c r i t i ca l  flow velocity 
and the degradation level ,  and these are a function of f i l t e r  mesh s izes  and 
clearance specification of component pa r t s .  
. 503 
TABLE I. - THERMAL STABILITY OF UNSHEARED ANTIMIST FUEL 
Temperature, Parent f u e l  Fue l  con ta in ing  a d d i t i v e  
"C 
Deposi t  D i f f e r e n t i  a1 Deposi t  D i f f e r e n t i a l  
code pressure, code pressure, 
mPa (mm Hg) mPa (mm Hg) 
- --_---_-__ 2 30 1 0.53 (4.0) 
245 1 7.3 (55)  - ---------- 
2 60 4 6.8 (51)  1 0.03 ( 0 . 2 )  
4 .07 ( . 5 )  275 
- ---------- 4 .13 ( i . 0 )  2 90 
3 20 - 
- __-__--__- 
--------- 4 .20 (1.5) - I 
AND FUEL CONTAINING NO ADDIT IVE 
Fuel  
~~ 
Breakpoint  F a i l u r e  
temperature, mode 
O C  1 i 230  - 245 1 A P  I 
275 - 290 Deposi t  code 
1-Pas s 260 - 275 Deposi t  code 
Undegraded 260 - 275 Deposi t  code 
TABLE 11. - WATER SOLUBILITY TESTS 
[ P a r t s  pe r  m i l l i o n ' ]  
uns heared 
Before t e s t  
A f t e r  t e s t  60 - 64 40 
504 
(b) Undegraded a n t i m i s t i n g  f u e l .  (a) J e t  A. 
Figure  le--- Comparison of spray p a t t e r n s  wi th  JT8D product ion-pressure 
atomizing nozz le  and Jet  A undegraded a n t i m i s t i n g  f u e l .  
(a) Jet  A. (b) Degraded FM-9. (c) Undegraded EN-9. 
Figure  2.- Spray p a t t e r n  with s t anda rd  JT8D engine  a t  i g n i t i o n  cond i t ions .  
505 
(b) Degraded FM-9. (c) Undegraded FM-9. (a) Jet A. 
Figure 3.- Spray p a t t e r n  with JT8D low-emission engine a t  i g n i t i o n  condi t ions.  
(a) J e t  A. (b) Degraded E'M-9. (c) Undegraded EN-9. 
Figure 4.- Spray p a t t e r n  with JT8D air-boost  engine a t  i g n i t i o n  condi t ions.  
506 
0 JET A 
l l 0 E  O A M K  
r\ 
Lf 
n 
W 
n v 0 
100 ~ 
90 
80 
K, CYCLE/M3 70 
60 
W FLOW RATE, kglhr 
50 K CYCLE PER METER3 
40 SG SPECIFIC GRAVITY 
F 
30 
FREQUENCY OF TURBINE METER, Hz 
0 1.00 2.00 3.00 4.00 
FREQUENCY TO VISCOSITY RATIO, Hz/cm2/sec 
Figure 5.- Calibration curve for No. 8 turbine flowmeter. 
4 -  
FUEL 
> 0 JET A 
0 > 
I- 
0 80 160 240 320 400 480 
kg /h r 
I I I 1 1 I 
0 200 400 600 800 lo00 
FLOW RATE, lblhr 
Figure 6.- Calibration data for a micrometer mass flowmeter. 
507 
0 
kglhr 
0 10 20 30 40 50 60 70 
FULL FLOW RATE, lbmlhr 
I I I I I I I I 
F igure 7.- E f f e c t  of an i tmis t ing  add i t ives  on 
heat t r a n s f e r  i n  fuel-oil  cooler tubes.  
UNDEGRADED 
3-PASS 16-PASS 
AMK AMK AMK JET A FUEL 
I I I I I IIII I I I I I 1 1 1 1  I I I I l l 1 1 1  1 1 I I I I l l 1  
.1 1.0 10 100 
1031 . 01 
su PERF IC IAL FLOW, cm3/sec/cm* 
Figure 8.- Degree of AMK degradation as funct ion of s u p e r f i c i a l  flow 
ve loc i ty  and d i f f e r e n t i a l  pressure. 
508 
40 6olb BATCH I 
SCREEN MESH FILTER TEST n 
BRITISH ORIFICE CUP TEST 0 
20 ASTM CAPILLARY TUBE TEST 0 
0 4 8 1 2 1 6 2 0  60 120 
TIME IN BLENDER, min 
BATCH I1 
rn * 
0 
Figure 9.- Correlation of three viscosity measuring devices. 
60 
50 
40 G 
a 
z 30 
o_ 
a 
E 
LL 
I- 
E 
l- 
E - 9 0  
LL 
10 
0 
I, 
1 
CONDITIONS: 
PUMP SPEED, r p m  
FUEL FLOW, kghr (Ibmlhr) 
DISCHARGE PRESSURE, MPa (psig 
0 0 
2400 3000 
750 11650) 1600 (3500) 
2.06 (300) 3.44 (500) 
 1 2 3 4 
NUMBER OF PASSES 
THROUGH JT8D FUEL PUMP 
Figure 10.- Typical antimisting kerosene (AMK) shearing characteristics 
filter ratio (AMK time to Jet A time through 17-pm screen) sampled 
at collection tank. 
509 
aAS JET A. 
r 
70 
z 
30 
.IN8 .010 .012 .014 .016 .018 
FUEL AIR RATIO 
Figure 1 1  .- Comparison of degraded antimist ing kerosene (AMK) 
with Jet A f u e l ,  tes ted  i n  JT8D nozzles .  
FUEL 
0 JET A 
@ 3-PASS A M K  
8 
NUMBER OF BURNER C A N  LIGHTS 
Figure 12.-  Sea-level i g n i t i o n  behavior for antimist ing-kerosene (AMK) 
and J e t  A fue ls .  
51 0 


The use of AntiMisting Kerosene (AMK) in turbojet engines

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