Aircraft fuels at low temperatures near the freezing point. The principal objective was an improved understanding of the flowability and pumpability of the fuels in a facility that simulated the heat transfer and temperature profiles encountered during flight in the long range commercial wing tanks

Stockemer, F. J.

English

NASA Technical Reports Server

LOW TENPEFiATUU3 FUEL BEHAVIOR STUDIES 
Francis J. Stockemer 
Lockheed-California Company 
An experimental investigation was performed by the  Lockheed-California Companp 
t o  study a i r c r a f t  fue l s  a t  l o w  temperatures near the  freezing point. 
pr incipal  objective was an improved understanding of t he  f lowabil i ty  and 
pumpability of the  fue l s  i n  a f a c i l i t y  t h a t  simulated the  heat t r ans fe r  and 
temperature prof i les  encountered during f l i g h t  i n  the  long range commercial 
wing tanks. 
The 
A t e s t  tank simulating a section of an outer wing entegral  f u e l  tank, approxi- 
mately ful l  scale  i n  height, was designed and' fabricated,  
construction included s t r ingers ,  scavenging ejectors ,  pump i n l e t  surge box, 
and other de t a i l s  corresponding t o  an airplane wing'tank construction. The 
t e s t  tank was ch i l led  through heat exchange plates  on the  upper and lower 
horizontal  surfaces. Other surfaces were insulated, A viewing port  was 
in s t a l l ed  i n  each v e r t i c a l  panel. Figure 1 shows a cross-section of the  
apparatus. 
Figure 3 i s  a view of t he  lower portion of the completed tank; thermocouple 
rack 2 i s  a t  t he  center. Table 1 designates thermocouple locations.  
Fuels used during the  program included commercially obtained J e t  A and Diesel 
D-2, a special  JP-5 type derived from o i l  shale, paraf f in ic  and naphthenic 
Jet A ,  Diesel D-2, and intermediate freeze point fue ls ,  and the  paraf f in ic  
intermediate t rea ted  with a pour point depressant; these fue ls  a r e  itemized 
i n  Table 2. The pour point depressant and most of t he  fue ls  were furnished 
through the  Coordinating Research Council (CRC) Group on Low Temperature 
Flow Performance of Aviation Turbine Fuels. 
Internal  tank 
Figure 2 i s  a photograph of t he  t e s t  tank during f i n a l  assembly. 
Tests were generally conducted by ch i l l ing  the  tank skins t o  a nearly constant 
temperature. During cooldown, cross l igh t ing  provided v isua l  evidence of 
convective currents i n  the  fue l ,  
f l o w  a f t e r  the  f u e l  reached a desired temperature with time, Suspensions of 
so l id  f u e l  pa r t i c l e s  were readi ly  withdrawn and presented no obstacle t o  f low.  
The accumulation of so l id  pa r t i c l e s  remaining a t  t he  bottom of the tank, a f t e r  
t he  l iqu id  was withdrawn, was defined as gravi ty  holdup. For cases where lC$ 
or  l e s s  of the  f u e l  was held up, the  holdup was essent ia l ly  a so l id  deposition. 
A t  greater  holdups, entrapment of l iqu id  f u e l  within the  matrix of so l ids  was 
discernible, 
t he  lower s t r ingers ,  then began t o  form on the upper surfaces and v e r t i c a l  
panels. A t  large holdups, accretions on the  walls and upper surfaces some- 
times f e l l  and could obstruct gravi ty  f low,  
Fuel was withdrawn from t h e  tank by gravi ty  
Solid buildup commenced on the  bottom of the  tank, spread over 
Temperatures measured a t  t h e  approximate locat ion of a commercial a i r c r a f t  
fue l  temperature probe (10 centimeters or above) provided a good measurement 
of bulk temperature, but ignored lower temperatures near the  chi l led w a l l s ;  
*NASA Contract mS3-20814 
221 
https://ntrs.nasa.gov/search.jsp?R=19800020829 2020-03-21T03:28:07+00:00Z
t h i s  effect  is  i l l u s t r a t ed  i n  Figure 4, Tests were a l s o  conducted a t  a vary- 
ing wall  temperature schedule, with f u e l  withdrawal occuring over t he  f inal  
3-hour period to represent an extreme cold condition, long range f l i g h t ;  t h i s  
schedule i s  shown i n  Figure 5, from data i n  Reference 1. 
J e t  A fuels ,  a l l  f u e l  could be withdrawn, but there  was evidence (from tem- 
perature gradients) of some sol id  formation a t  t he  time of minimum temperatures, 
and subsequent melting of the  sol id  material. This is i l l u s t r a t ed  by the 
sequence of temperature prof i les  shown i n  Figure 6. 
Sloshing, recirculation, and use of e jectors  tended t o  decrease the  temperature 
difference between the  chi l led walls and the bulk fue l  and ind i rec t ly  affected 
t h e  holdup by a l te r ing  the  temperature prof i les ;  t h i s  e f fec t  i s  seen i n  Figure 7. 
Tests with an in te rna l  baf f le  or with dehydrated f u e l  showed no change from 
comparable baseline t e s t s .  
With specification 
Tests with an intermediate d i s t i l l a t e  fuel ,  t reated with the  addition of a 
sui table  pour point depressant, provided a s ignif icant  reduction i n  gravity 
holdup, compared t o  tha t  of the  undoped fuel,  
ule, the  t rea ted  f u e l  (No, 7) produced 10.2% holdup, compared with 25.5% for  
the untreated LFP-5 fuel. Tank results agreed with laboratory data reported 
by the  manufacturer of t h e  additive. 
For the  same temperature sched- 
Figures 8, 9, 10, and 11 i l l u s t r a t e  varying quant i t ies  of holdup. 
Table 3 itemizes temperatures pertinent t o  freezing and subsequent gravity 
holdup, 
Figure 12 shows the change i n  temperature a t  a specif ic  height fo r  various 
holdup quantit ies.  
i n  a temperature greater than freeze point, 
controll ing t e s t s  So a s  to produce variations i n  gravity holdup. 
Extrapolation of the  curves t o  zero holdup always resulted 
However, the  effect  was useful i n  
This experimental investigation provided considerable insight in to  the  behavior 
of fue l  a t  l o w  temperatures representative of f l i g h t  conditions. A ra ther  
large quantity of t e s t  data was obtained which could furnish material f o r  
further analysis. 
Results of t h i s  investigation a re  reported i n  NASA CR-159615 "Experimental 
Study of Low Temperature Behavior of Aviation Turbine Fuels i n  a Wing Tank 
Model". References 1, 2, and 3 provide additional information re la t ive  t o  
the use of aviation fuels  a t  l o w  temperatures. 
REFERENCES 
1. Pasion, A. J., and Thomas, I, "Preliminary Analysis of Aircraf t  Fuel Systems 
for use with Broadened Specification J e t  Fuels" NASA CR-135198, May 1976. 
2. Pasion, A. -J, "In-flight Fuel Tank Temperature Survey Data" NASA CR-159569, 
3. Pasion, A. J, "Design and Evaluation of Aircraft Heat Source Systems fo r  
WY 1979. 
Use with High-Freezing Point Fuels" NASA CR-159568, May 1979. 
222 
TABLE 1 
DESIGNATION OF THERMOCOUPLE: LOCATIONS 
No. 1 
No. 3 
No. 7 
NO. 8 
LFP-1 
YP-3 
LFP-4 
m - 5  
WP-6 
WP-7 
[EIGHT AZ 
Cm. 
0 
0.6 
1.3 
2.5 
5.1 
10.2 
20.3 
25.4 
30.5 
40.6 
45.7 
48.3 
49.5 
50.2 
50.9 
Jet  A 
Distillate 
(Diesel D-2) 
Intermediate 
with Additive 
JP-5 
Je t  A 
D5stillate 
Dist i l la te  
Intermediate 
Intermediate 
Dist i l la te  
E BOTTOM 
In. 
0 
0.25 
0.50 
1.00 
2.m 
4.00 
8.00 
10.00 
12.00 
16.00 
18.00 
19.00 
19-50 
19 75 
20.00 
LFP-8 
LFP-9 
E 
1 
- 
2 
3 
4 
5 
6 
- 
7 
8 
9 
10 
11 
- 
12 - 
Jet A 
Jet A 
I N 1  
Rack 2 
13 
- 
14 
15 
16 
17 
18 
- 
19 
20 
21 
22 
23 
24 
- 
4L m. 
Rack 3 
25 
- 
26 
27 
28 
29 
30 - 
31 
32 
33 
34 
35 
36 
- 
Rack 5 
44 
- 
- 
45 
46 
47 
48 
49 
- 
- 
- 
- 
- 
- 
50 
T58 t 
Rack 2 
13 
14 
15 - 
16 
17 
18 
- 
19 
20 
21 
22 
- 
23 
24 - 
u 100 
Rack 3 
25 
26 
27 
28 
29 
30 
- 
- 
31 
32 
33 
34 
35 
36 
- 
Thermocouples 51, 52, and 53 a t  centers of tank walls (fixed panels). 
Thermocouples 54 and 55 on upper skin each s ide of longitudinal center. 
FUEL TYPE FUEL XS)lWJ?IF'N. 
I I 
CRUDE SOURCE 
unknown 
unknown 
Paraffinic, 
Same a8 LFP-5 
Shale Oil 
Paraffinic 
Paraffinic 
Naphthenic 
Paraffinic 
Naphthenic 
Paraffinic, 
Same as LFP-1 
Naphthenic, 
Same as  LFP-6 
Paraffinic, 
Same a8 LE'P-3 
APPROX. FREEZE 
-44 
+ 2  
POINT, OC 
-31 
-34 
-41 
-17 
- 14 
-28 
-28 
- 10 
-52 
-46 
APPROX. F q L  
BOIL. PT., C 
257 
326 
294 
261 
267 
314 
346 
295 
282 
316 
263 
255 
SPECTFIC 
GRAVITY, 15OC 
0.8132 
0.8612 
0.8294 
0.8029 
0.8017 
0.8285 
0.8545 
0.8299 
0.8478 
0.8251 
0.8273 
0.8001 
223 
TABW - 3 COMPARISON OF SOLD-LIQUIl) TEMPERATURES 
Average Freeze 
Point (from 
Appendix A) 
NASA Freeze Point 
Shell Cold Flow 
Test, Zero Holdup 
Shell Pour Point 
Loclrheed Pour point 
s olid/Liquid 
Interface 
L FUEL e 1 NO. 3 
-38 -14 
-52 -21 
-47 -24 
- 
FUEL 
\lo. 1 -
-31 
-46 
-45 - 
-16 
-24 
-37 
-26 
- 
FUEL 
No. 8 
-30 
-30 
-32 
-38 
-34 
-37 
-33 - 
-29 
-30 
-36 
-38 
p(IELIFuEL 
VP-1 LFP-3 
-7 
-15 
-18 
-18 
-41 -17 
-42 -19 
-43 ~ -15 
-51 -27 
-44 -20 
-47 -30 
LFP-4 YP-5 
~ 
-22 I -31 -32 1 -12 
- 
FUEL 
WP-e -
-52 
-53 
-54 - 
- 
FUEL 
YP-9 -
-46 
-45 
-45 
-48 
-48 
-li6 - 
 AI^ temperatures in  OC> 
224 
DI 
Cf 
COOLANT (TYP. 1 VENT 
I . r EJECTOR (TYP. 1 
ISCHARGE PUMP 
DISCHARGE TO 
WE1 GH I NG TANK 
Figure 1. - Cross-section of apparatus. 
Figure 2 - T e s t  Tank During F ina l  Assembly, End Panel Removed 
225 
Figure 3 - Looking Through Fuel i n  Tank A t  S t a r t  of Test 
226 
I O.”$ Gravity Holdup 
E-c 
m 8 25 
T/C Rack No. 1 -- - T/C Rack No. 2 
T/C Rack Eo. 3 
----- T/C Rack No. 4 
------T/C Rack No. 5 
--e- 
-50 -45 -40 - 35 -30 -25 -20 -15 - io  
0 TEMPERA’M3R.E- C 
Figure - 4 Tem-peratvre Distribution a t  End of Test 75 
227 
0 1 2 3 4 5 6 7 8 g lo 11 I2 
FLIGHT TIME - HOURS 
Flgme - 5 Temperature Schedule f o r  Scheduled Withdrawal Tests 
228 
I 
55 
50 
45 
40 
35 
30 
25 
20 
15 
10 
5 
0 
Figure - 6 Temperature P r o f i l e s  at Center of Tank, T e s t  94 
Scheduled Withdrawal, LFP-9 Fuel 
229 
-55 -50 -45 -40 -35 -30 -25 -20 -15 
T S M p E R A m  - OC 
Figure - 7 Temperature P r o f i l e s  from Center of T ~ K  at End of  Tests - 
Fuel  LFP-9 
230 
Figure 8 - Gravity Holdup of 3.2% a t  End of Test 73, LFP-9 Fuel 
~ _ _  ___ 
Figure 9 - Gravity Holdup of 4.5% at End of Test 46, LFP-7 Fuel 
231 
Figure 10 - Gravity Holdup of 8.8% a t  End of Test 41, LFP-6 Fuel 
Figure 11 - Gravity Holdup of 57.2% a t  end of Test 36, LFP-1 Fuel 
232 
OV 
I 
9 a 
2 
c, 
8 :: 
d 
c, 
Id 
$1 
I 
233 


Low temperature fuel behavior studies

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