High-speed motion pictures were taken of fuel sprays injected into the combustion chamber of the N.A.C.A. combustion apparatus. Three fuels, ethyl alcohol, gasoline, and fuel oil, which differed considerably in volatility were tested. By maintaining the engine temperature below that required for ignition the spray could be studied from soon after the start of injection until 130 crank degrees later. The results show that the sprays vaporize appreciably so that it is possible for the ignition in high speed compression-ignition engines to take place from the vapor phase

Rothrock, A M

English

NASA Technical Reports Server

070101 
TIlC:-EH CAL :~O TE S 
liATIOHAL ADVISORY CO~::IE' TS~ j' OR .AEROl~AuTICS 
lio . 408 
PRELIEHTARY TESTS OH THE VA?ORIZATIO~; OJ;' _ UEL SPliAYS 
By A. ~ . Rothroc~ 
Langley ;:0r:lorial Aeronaut ic al Laboratory 
IT as ... 1 hl .": t 0 ::1-
}'ebruarr , 1932 
REPRODUCED BY 
NATIONAL TECHNICAL 
INFORMATION SERVICE 
u. S. DEPARTMENT OF COMMERCt 
SPR INGFIELD, VA. 22161 
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HATI01-iAL ADVISORY COMMI TTEE FOR AERO :::TAUTICS 
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. i 
TECHNICAL NOTE NO. 408 
PRE!.IMHTARY TESTS ON THE VAPORIZATION OF ~UE:S SPRAYS 
By A. M. Rot~rock 
High-sp'eed motion pictures were tak en of fuel spray s 
inj'ected £ni; t~e combustion chamb er of the N.A .C.A. com-
bus t ion ' app ar ,atus . Thr ee fuel s, ethyl al co ~10 1, ga s o l i 11e , 
-an d fuel oi 'I ', which dI f fered consider a blY in volatili ty 
were tested. By maintaining the eneine te mp erature belou 
thatreq~ir~d f or ignition the spray coul d be studied fro~ 
soon aft~r ~he sta~t ~f ' injection until 130 crank de g r ees 
l 'ater. ' ' T ~le resul t s show that the spr ay s , :vap orize appre-
ciably so that it is p o ssible for the ignition in hi gh-
speod compressi on-:-i gniti on engines to take ' p l ace ' f ro ;u t il e 
vapor p~'as 'e ' . ' 
IHTRODUCTION 
Preli minary results obt a in ed with the N.A.C.A. com-
bustion apparatus (reference 1) indicated t:lat there was 
marked vap orization of t h e f uel duri ng a n d f ollowin g its 
injection into highly heated an d d e ns e air . As this phe -
no monon should havo an a pp reciable e ff ect on the co mbu s -
tion of tho fue l, particularly under tho co ndi tions which 
cause comb u stion shock,' a seri e s o f tosts WEi. S outlined to 
investigate ful ly the vap orization of the fue l spray. T:lC 
purpose of this note is to p re.sent tho f irst results OD -
tained in these tests. The n ote is to b e follow ed by a 
report wh ich will discuss the vap orization [l.:1d its o ::.f o , t 
on-c~mbustion in more detail. ' ' 
METH ODS JtNTI APPARATUS 
The N.A.d .A. co mb~ stion a pp ar atu s was nsed i n , the i n -
vesti g a ti on. The, appar atus y onsi s ts of , a. sinG,le-cy U .nde r ' 
test en c i n e and a n injection syste~ togethe r with a hi G~­
speed motion p ic t ure apparatus. The co mpr ession rC\tio 0-: 
·-' 
2 IT .A. C . A . Technic{,,-.1 Note Eo •. 408 
the ens ine is 1 5 . 8 :1 • . Tb.e 'sides of the : combustion chaD-
be r of t h e e n gine a re f ormed by g la ss windows through 
\Vh ic l~ t1.1e phot o g r ap hs are ' t;;u:en. ' In the operation of tlle 
ap0 D.ratus the engine is d rive l.l " a t the desired sp eed by a n 
e l e ctric mo tor . ~y means of a suitable clutch a sing le 
Cll E'.r u; e of fue l is injected intq . tlf~ combustion chamber o f 
t lle o11::; ine duril1 g the compression stroke or the first p 2.rt 
o f L.e exp ansion str ok e . At the s am e ti me that t h e in-
jo ctio~ is t a~ i ng p l ace h i gh- sp ~e d motion p ictures a re ta~­
en of t~:l.0 f 1.1.e l sp :;,·a~r. In the p re s e n t series of t e sts 1 3 
p ic tures were t aL on 2. t the r ate of 1, 00 0 per s ocond . • Th o 
p :'1 0 to g r ap h s w e rot i rod r e,l a t i vet 0 tho p o sit ion " 0 f . the 
crc.:r.J.k~h<?-f~ .9f· tho eng ine b y means .o f ·ail electric sp.ark; • . . 
J: ~1 8 t e ;lJ:p e r 0tur~ of the i:; lyc er in circulated in th e head s . 
and c y li n d e~ j~cket o f th~ engine was ill~intained a t 1 00°F . 
t ~roughout t h e tests , so th~t combustion of t ~ ~ injected ' 
fue l would , not t8J~e p l a ce . Conse quently , 'at the eng ine 
spe ed U S?~ in thes~t~stsr 1 , 500 · r . p . m. , t he p hysical 
c~(,me; es ~n · t he fit at e' ,o f the :;:'ue l co u l d b e s t udied over ' an 
i n t e rv a l of 1 3 0 ' cr~nk degr ees . 
Th e injection pressure was 4, 000 p ounds ~ ~r , s quare 
inc h , t ~e injection valve op e n i n g p re ssure 4, 0 0 0 p ou n d s 
p er sQ'l a re inch , a nd t h e initi Cl. l p r essure in the injection 
li n o be f ore i ~jection 1 , 000 po u nds p er square inch . 
DISC1.YSSIOI-i" ' AND TEST ", ESlJLTS 
Ethy l alcohol , ~a sol i ne , a nd f u el oi l were u sed in 
tile p r esen t tests . T> ese fuels we 0, cnosen b e cause t h ey 
d i !.f e~ o d conside r a bly in volati l it y . (Se e fig . 1.) If 
the f-clels clid vap o r ize in the co mbu stion chamber of the 
811 .; i :;.:,e , the :t? oin t a t w"tich the cond ens a tion of the v ap or 
o cc~rr o d sho u ld vary co n sider a b l y d~pending on the boil- -
i ~~ p oin t or boi li n g · rang e of the f u el. Proof of this is 
s :l o,\7n i n F i g-ues 2 , 3 , and 4 ~ An e x a.mination o f the fi {.; -
ure a s l10wr; t :1at as the :,:~ ue l C.?.me i nto t~1 e cOI!ll)ustion cham-
b er t ~e si l hou ette o f the sp r a y Wa S recorded on the photo -
g raphi c f il !!1 . The sp ray ' th e n d is t~.pp e~.red. , or tend ed to 
d is~J~ear , ~ol lo w i n g the cut - off of injection, So me ti me 
af t e r tO Il cen t e r t h e fu el wh ich had vap orized conden se d , 
. bl ock inG out the li ~ht irom t~e spar~ . d ipqhar g~s so t h at 
n o li s ht , or very lit t le , 'was recorded on t h e . p hoto g r aph.ic 
f il i!l . 0:2 each fi gure a l i ne ha s bee n '. drp.wn t h roug h e.ll 
tlle re c ord s to indi c a te , top· center. A second line h a s been 
• 
I I 
"' , 
;;;.A,C. ·A. Technic a l Fotq .. l!o~ '1:08 
. .. . . 
3 
drawll. tlV:~>ugh t.he ;l ,a.s.t , p'h otogr(~,ph ",f t ·ar top C(Hl.to·r :i T • . " .. : 
which n,o, ·.fuel · ap.;pea'i;ed ~ w'itil , injecttO!l starting <l.t 50 0 or 
40 0 oefo'r .E;), .top center. ' It w,ill be noticed that t ile' spar1:: 
dischirge~< ·were retarded so that- the :first photograph 172, S 
ta~en n~~r or at t~~ end of injection. This was done so 
that a l on ge r interval on the expansion stroke could be 
studied. 
When ethyl alcohol was used, the vap orization was 
.quite compl,ete as indic ated by:, .tJle clear. :L maf;es or the 
co mbust ion chamber following injection. T4e condensatidn 
to .. ok p, lace betwee.n 50 o .and 60·o ar'ter top , cent e r, tho ex-
acit time depend~ng . ~ome~h~t on the i njection advance an-
gle (I,A .A. ) . W{~h injection starting at 50° befor~ tOTI 
center t~le vaporization was practically completed at lOll 
before top center as is indicated by the clear p~otoeraphs 
o f the image of the combustion chamber . Pa~ticula~ly note-
worthy is. Xh.e sp~,ed · with which the condensation took p ln.ce 
as is sh'own , by , th~ ·, ·sv-dd. en blocking out of the 'li ght fro m 
the conden~er di~~hargei bet~~e~ ~5° and 60 0 after top 
center. The same is true with injection starti ng at 40 0 
before top center. With injection starting a t 30°, 20 0 , 
and 10° before top center-.: al1d.· at .. top center the cOn(len8n-
ti o n b ecomes less rap id, ~s is indic ated ~y the photo-
graphs in which some Ool the condensate is shown althol '.. g h 
the light ., is not comp le~~~y.~~ocked o~t. , 
.' " 
With ~aso line clear images of the combustion chamb er 
were als o' 6b 'tained, indicating that va'p orizati~m , must 
still have been quite cOi1l!J lete a lthough the condonsation 
was le ss rapid . Con d ensation occurred , howevor, earlier 
in t ;le expansion stroko (at 42 0 after top centor). ~i th 
injectio n starting at 80 0 and 70° before top center the 
photo ~raphs show that t h e f uel spray d iffused , almost 
fillin~ the chamber, and then vap orized, condensi ng on the 
ex-pansion stroke. 
\,H th the fuel oil the val)orizatiol1 was less r ap id a11 .. l1. 
the c on den sation occurred still earlier in t he strgko ( at 
27 0 after top center with injection starting at 50 before 
top center). In no c as e was the v 3,p orization comp lete 
with injection startin g b etween 40 0 b efor~ and at top cen-
ter . Uith injection starting at 50 0 beforo top center the 
fuol diffused completely t'hron(~h tho chanD er, blocki ng out 
all tilO light, and then vaporized. 
A comparison of al l the figures sholls that, u.nder 
tile conditions o f opero. tion of high-speed comprossi on-
4 N . A~C . A . ; Tq chn i cal Npto No. 408 
. ' 
igniti on e ngines, f~e l sp r ays ,will vapori~c during ~nd 
f ol low~n~ t h ei~ ' i ~ j e c t~ bn i nt o t~e e~~inri ' a~d that this 
vapor i z a ti on t Clk e $ place ' E? v e n thO UgJ.1 tho t e r~ "') craturo in 
tIle e n gin e ' is n ot ' ,suff i cion t " to c a;tis c cQ rnbu 'stiol1, 
. .~ 
CONCLU S IONS 
' Th~ t es t re ~ul t s pf e sen t~d " s~ow ' t~~t : f;~l sp rRys , in -
jected i n to th~ ~ o ~b~stf o n , cha~b~r of ~ ' compres~ion- igni­
ti ori e ngi ne vap orize a pp r e ci ab i y so that the combustion ' 
can -p roc~ ed f rom the : vap or p h as e instead o'f from the l i q.u id 
ph<:-s~:. ' -,' , 
'Langley MeU; ori a l 'Ae ron a u t ic a J, Laboratory, , 
Na tion c;l. l Adv is or y Committee fQr Aerori Ltuti,c 's; 
Lan gle y Fie l d ', , Va . , January 2i, "1 932.'· 
. " ; .' 
REFERENCE 
" 
• .' r 
4 .. ' .. '. 
1 . Ro t hrock , A. M.: :rh e .i'LA. C.~~' ; App ~ratu s for Studying 
the F orma ti on an d Combustion of Fue l Sp r a ys and 
, , ' 
the Re sults f rom . Preli mi narY , Test~ . T.N. 389 , 
N • A . C • A., 1 9 3 1 • ' ':' :: 
'. " 
'- ' 
~ . 
,, ' 
', .. .... 
• 
• 
N.A.C .A. Technical Note No. 408 
~ 
Q) 
~ 350 .-
~ 
cO 
H 
C) 
~ 300 
Q) 
8 
70 80 
Percentage distilled 
Fig . 1 Di stillation curves of fuels tested • 
Fig . 1 
90 100 
4 
• 
z 
• 
I.AA, O' ~ 0 
· > 
· 
8 
~ () I.A.A., 10' 
P'" 
::s 
.... 
() 
I. A.A., 20' e 
z 
0 
~ 
~ 
Z 
0 I.A.A., 30' 
• 
~ 
CD 
I.A.A..40' 
lA, A ., 50 1 
1;0 do lJoATC 
17me , Cn:3nKMOrl d'J'rees 
t:.;j 
.... 
Fig. 2 Vaporization of ethyl alcohol. Engine r.p.m.,1500. Engine temperature,lOOoF. 
Fuel quantity, 0.00025 pound. Discharge- orifice diameter, 0.020 inch. 
()'q 
• 
t\) 
~ 
L 
• 
I. A.A., O· 
I. A.A" 10" 
I,A.A. , 20" 
I, A.A.,-'O· 
I,A.A, / .fa" 
I.A,A·ISO· 
~A.A'l60· 
I. A.A •• 70 " 
I.A.A,/ l!JO ' 
70 
"''' 
..0 100 
17m. f cr4""K~' " ~r' .. . 
Fig. 3 Vaporization of gasoline. Engine r.p.m.,1500. Engine temperature, 100°1. 
~ Fuel quant i ty, 0. 00025 pound. Discharge-orifice diameter, 0.020 inch. 
110 Iko 
~ 
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o 
o 
· > 
· 8 
(I) 
~ 
~ 
() 
e. 
~ 
o 
C't' 
(I) 
Z 
o 
~ 
co 
~ 
~ 
• 
~ 
• 
I.AA" O· 
f.AA., 10 · 
f.A.A., 2 0 • 
f.A.A" 3 0 · 
I.A.A., 40· 
I.A.A., 50 · 
I.A A., 6 0 · 
I.A.A., 70 · 
I. A A., 80 ' 
60 7b "0 90 
~ 
Fig. 4 Vaporization of fuel oil. Engine r.p.m.,1500. Engine temperature, 100°F. 
Fuel quantity, 0.00024 pound. Discharge-orifice diameter, 0.020 inch. 
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Preliminary Tests on the Vaporization of Fuel Sprays

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