End-zone water injection as a means of suppressing knock in a spark-ignition engine


Material Information

End-zone water injection as a means of suppressing knock in a spark-ignition engine
Alternate Title:
NACA wartime reports
Physical Description:
8, 5 p. : ; 28 cm.
Brun, Rinaldo J
Olsen, H. Lowell
Miller, Cearcy D
Aircraft Engine Research Laboratory
United States -- National Advisory Committee for Aeronautics
Aircraft Engine Research Laboratory
Place of Publication:
Cleveland, OH
Publication Date:


Subjects / Keywords:
Airplanes -- Motors   ( lcsh )
Spark ignition engines   ( lcsh )
Aerodynamics -- Research   ( lcsh )
federal government publication   ( marcgt )
bibliography   ( marcgt )
technical report   ( marcgt )
non-fiction   ( marcgt )


Summary: An investigation has been made of the effectiveness of water injection into the combustion end zone of a spark-ignition engine cylinder for the suppression of knock. Pressure-time recoreds obtained show that injection of water at 60° B.T.C. on the compression stroke at a water-fuel ratio of 0.3 rendered M-3 fuel as good as S-3 fuel from an antiknock consideration. The optimum crank angle for injection of water into the end zone was found to be critical. As the injection angle was increased beyond the optimum, the quantity of water required to suppress knock increased to 3.6 water-fuel ratio at 132° B.T.C. The water quantity could not be increased beyond 3.6 water-fuel ration because of injection-pump limitations; however, a further increase in the injection angle up to the earliest angle obtainable, which was 20° A.T.C. on the intake stroke, continuously increased the knock intensity. The engine operating conditions of the tests did not simulate those encountered in flight, especially with regard to the operating speed of 570 rpm. For this reason the results should only be regarded as of theoretical importance until further investigation has been made.
Includes bibliographic references (p. 7-8).
Statement of Responsibility:
by Rinaldo J. Brun, H. Lowell Olsen, and Cearcy D. Miller.
General Note:
"Report no. E-72."
General Note:
"Originally issued September 1944 as Restricted Bulletin E4I27."
General Note:
"NACA WARTIME REPORTS are reprints of papers originally issued to provide rapid distribution of advance research results to an authorized group requiring them for the war effort. They were previously held under a security status but are now unclassified. Some of these reports were not technically edited. All have been reproduced without change in order to expedite general distribution."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 003636147
oclc - 71757503
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Full Text

I/ICA C-7k

RB No. E4127


September 1944 as
S:Restricted Bulletin E4I27


S By Rinaldo J. Brun, H. Lowell Olsen, and Cearcy D. Miller

Aircraft Engine Research Laboratory
S"Cleveland, Ohio

Afi ,,; : C WARTIME REPORTS are reprints of papers originally Issued to provide rapid distribution of
:i:aince research results to an authorized group requiring them for the war effort. They were pre-
,io 'i .i fly held under a security status but are now unclassified. Some of these reports were not tech-
Mi l. 0I edited. All have been reproduced without change In order to expedite general distribution.


jrj ;



-17 5 7 5 c)
; 30/7

I!ACA RB No. EhI27





By Rinaldo J. Brun, H. Lowell Olsen, ani Cearcv D. L.iller


An investigation has been r.ile of t.ie ff.rfti',-'ness orf iter
injection ino "'.e combl:ustion e::a none .;: a sp;rl, -i.-"ition engine
cyli:.:ler for the suppression of i'ick. P]re.:-uire-tLj.mc r-:'is
obtsinei show that injection 1f" a'it.r at L. 60) B..T.C. on JIi cr';,-
Dressionl tr-ke at a .at.~-!.. r-ti of 0.9 reF niler-e.! L-. I:F- as.
cood as S-3 fuel from an a-1t. i ,::iri e ri .i. TI-r ; tii um
crank an..le for iujecr:.io, j -:. in t. th, e *--1'. I zo:e w S ;:..ind t..)
be critical. As t;ic inject r .n-'e ;':;as incr:-,sc J D.' ;cni the
optimum, We qua!t it.y of i.at,.: .cquirod, to -im.ress knr: inc cased'
to 3.6 wat.r-ftuel r. Lti a.. 1'' P.i.C. Th;e waterr quartti.ty coul.
not be ilncreasei bDyo.-n, 5:. bvw, L,-r-iul rat.o "c,,c ause .:.i inject .on-
pump limitations; however, a 1 irt!!-'i i:irea.r-ir in tnJ injectCon
angle up uo Lhe earliest :nrle ,btairiabi:, wlhii was 2. ;,..F.C. on
the intake stroke, continulusLlV inzre:.sel th.- itock in.t...iit..

Th ertginre .jorati .f ccru:iii j.ais .fi' r' tr e t., 12 1 :iot simulate
those .ncuAnter-i in 1ii.ht, ,snor.c.aly wit r-'card to t:he oper-
atifiC speed of j7u rpm. For tLs r-_.n ti. :..Ilt ;hD.l.i only
be regard-d as oi' Lthejretical iTmportance until Lurthtr investipa-
tion has uden mane.

I L'TROD .:T T0:]

Tihi invustigat.,i n her in lescnib--d ', s ba.Festrat by observation
of highL-sjxeJ ph.- .,,'r.d,)hs '.: coa:')',i.1 -'.n :. ',orr-:-i nit ion engine
cylinder tken with t.:-.. '!jiCA hi, r.-spejd camera at th- rf.te nf
It.,0L1O frar.es pn'r sec ,:1 (refere-ncuL L;. T'lhe-: ;h)jtoflranIs con-
firmed the ,-c v.ilil..i n oni.;nin that th'- c!,:'Jr:ti..n ni zon-e involved
in the k:l-i'Ce re.cti-n ..:lu'--' only a Emnll ir.ictiiun .i' !-: rass
-r tLhe total cyll.nler char,:e. TILV ~,nt.a.ra.s al ;s i:dicted that
this small frr'ctiC on ,i' t:, mass 'f t'i t,'t.al char,'e 1.; o, ;-rcssc"I
into an :xtrer. ly S alJ.3l. a:nd w'ell-.ii.ne- voLurr,- ouefore hi uci occurs.


A study of the photographs suggest-Al that a great saving in anti-
knock additiv nmigiit b? effected by injecting the additive exclu-
sively int o the '-nJ zone, pr-sumnably tie only region in which it
1.3 needed.

Introduction of water into the combustion chamber of the
internal-conbustion Icnine for t.a purnos of s pressingg knock
Jr cooling of th- engine parts is v.ry olJ. In 1915 Hopkinson
(reference 2) reported successful re's-its cf extensive tests with
large gas engines with which th: cooling was entirelyy by water spray
on the inner surfaces of the comhustian chamber. In 1921 Clerk
(reference 3) indicated tnat he had used v;at-r to suppress extremely
violent knock in the year 1850.

kiore ruc-nt investigiLions of the effect of wvate-r arid other
liquijs intro:Luc.- int) the ful-'.ir mixture before ait.ission into
tue cylinder on rmozk-liritel and tF-rperatuir-li:iited power output
are described in rel'fcrnceo L anT' 5. The wat.-r or oth.-r liquids
used in this rr.-nncr care te.irmei; i; 'Li:rn-il coolant."

Ine object oi the tcsts repOr.:-1 i,-roin was t. deternrne the
valuco of i'jncct.i)r n ;: -.atar i:.tj 4h. *ni -7"e-, as an antitkock agent.
Thei eng..ne us,~ in thi-s tsts3 ouL no)t be sucezc';~.rped and the
inl].:t-air t m'xrrat ir. c.ul: '. r!t b- r-:is,,d a3bvc r23rm t-.lniperature;
thrrefjor,, t.ri? t'.fct.ivn:-Z.s ol urn: .at r was L-t-.rr.i:il-di by lowering
the r,taLncock val u of u' f'.i.l. 7 ie ,-n7ire ,-..eratJinr. speed was
far b.lowv, t.lhe sp:ed- ,.I.-d in lli;r.'. res'1ts sho-ld be consid-
or,: n a c r -.: ""
red only n a t.'(..cr-.tica l doa.i s ,il -"tn=r i..v'--sti,.ations have
been madJ i.r.. r- 1' 'E, ~... -na -ii, 0 >p: atjir -.:,.Jiti s of
fli7iit. Tis '!r-,i-. ir: P:rticu,.rIy irmprt,-tat cca6ise difficulty
may b- .:pe-i Ci .cel i.L a..'plyin. t:L '. t.'.od TJ Lf i. r-sDnt .d engline
,neraLi :1. i

Th tests were ncrfc.rrred at th- Aircraft Eni-inc Research Labo-
ratory of the Natl-onnl Advisory Comritw.e. ior irinait.ics during
late 191.i5 viid c-arly 19'Y..


The e.,rint isc,:l in ti. ,prE s:nt tesLs was the NACA combustion
aooaratuc dcsc ib. J in r:f'. ience 6. An in.i.ction valve was installed
in onT oft t.!.' 'yLu- icr up'niri;s to s;pr_.,' water r Lnto the last part if
ti chliar-e to burn. Photograpr.s weir taken w'ith t-he !ACA high-speed
cAm,.;rr t -)s.rv; t:v; ;. :xact -enrd-L-ni: po.jiti:n ani t-i': shape and the
eixt-:t t JI tni rc;,i. ,-..r,,-t -ti ja Lj',' tn water spray.

NACA RB No. Elh27 3

The; engine wss fired for one cycle only Jor coach test run.
An electric motor kept the engine speed constant until the firing
cycle occurred. a single-cycle clutch was enga;cd at the beginning
of the firing cycle between the engine crankshaft ani an accessory
shaft to inject a single charge of fuel i,,t t;he' cylirndler on the
intake stroke, ignite the charge at tn(, proper time, and inject
water at the ireletermined injection angle. The cylinder tnmoera-
ture was maintaini- by circulating hc-ate3 glcerin through the
engine jackets. Three spark :l'ae s were usei to bri.na the end zrone
into the desired ,.osition in i'r-'.t of L.tw atater-injection nozzle.
The ignit.ion :ji.:n:.;was 5 set that t'ie completion of burning. with
S-3 fuel cccurre.L :nar top center. Thre rater .13ueJ or injection
intD the cylinder was di:aerar,... in cri:r ti avol. th*: f': nation of
gas bubb;l.s in t :, ir.ject4 .n val'.e. T;e fuel-air ratio was set
sli,'htly rtic!-Ler .han that required for N;axi im; :-cl. .'ith S-5j fuel.
T'r;j va.Lves were; .:se -*7.. servi- .'or b:th i'.takE ani e:xcaust.
P e, -ssur.--t.-r.'e re'n'Jrs ;iert .t.ij -.e .1 b.; r...it.: 'r .t.ink -, 1ci11 -
sc-'ore screen. Tir- iinut to Le vertical nl.-ites ofl tt oscivllo:cone
was .iQjouzed ouy 'iezcilectri c :*ressLre iC_.-r' nctalled in the

Engine c'ro iiti')n heli1 c'nrit.a-t -;j're:

Engine speel, r-r,i .. ............... ... $70
Fuel injection (intake stroke), .!eprees A.T.C. ... 20
F Iel-air ratio ( .ppro:xi.a.-).. .... .. .... '. 'J.'i2
Cylin l er tn.inoriture-, }.. . .. 2!21 2
Co.mpi es ion: ratio . . .1
intake p'res3Jre . . atmospheric
Ex'iuust pressure . . at;nios -hric
Intake te'' .rat u'-, OF . (rom teoerature)
Spark timing, -degroes .T.C.:
EarLiest plUg .. . ... ..
Later i.. s . . 26_1

uE '.LT.. artJ )ISCUS'jS3io

A photograph of about one-!-al"' the c.nr.cuztio. co-.amr.ber at the
tiiime all the w atr s-jray/ al entered int' t.ie ,-hanbri is s..nvin in
firrire; 1. TTI .Iiish! I i. cle s'..JT3 thr c-a .busti'rn-chamber outline
:.s viewed Ir'):, thWe .o. 'L.'he letter C ir, th j -wurc i.-Ii.-i.ates the
positi-)n )f '.he eaSi:! z.t-fir. d .pari 2j1',', :i ani F the positions
of the later-fir- 1r't '1 -lu rs; J in-icates '.h1-. ::itiion c. the
water-inje-ction r''.) :., 4 t'; r,'siti.ij .-i, oi tl' fu'el-inje.?ti? n
n1r el rJ T th,: .I:itio A t.:- ie:.'electric r'ss ie ikun.

NACA P3 No. Ebl27

A photograph of the end zone a fev engine crank-angle degrees
before the end of c-mbuistion is shown in figure 2. The end zone as
seen in liiur,. 2 is somewhat larger than the knocking end zone under
the rost severe conlitioni ia:oosee in the tests. The photographs
in figures 1 and 2 are stigle frames from two series nf pictures
taken at 4OOUO iramies per second rith tne NACA high-speed camera
and slow the development of the water spray from the nozzle and the
burning of the charge in the chamber, respectively. in figure 2,
the water-cpray mitline obtained irorm 'iture 1 has been drawn in
to si. vw its luca'tio, "with rejnel;t. the end zone.

Pressure-time records of firing c-rcls r:re sh)wn in figures 3
to 5. Th- ljerre.t trace in eacn ii:.,ure is a r:.otoring trace taken
j', s beficrc tlc. [irir.p cycles.

The traces Af Lw.o consecutive firing cjcles sirzerinmosed on
the sane f.]:n are 5jic.-.: in figure 3. Ti.hL trace with the violent
!:no.k, JesignatuJd "ur.quenched 4-)" in the fi'urv, was taken vith
>i-5 luel .:ithout b.at',r inect'ion. The trace '.ith ircipient ktnjck
ani larg'-r area 'unir '.he trace, .-:!ai nated quenchedi L-j3" in the
figure, was taken ';itr. M-j fuel vi L I injecti r. of water at
L?3 b.T.C. on ti~ co. press.ioa strike. T.'e *c-ight .)f ,'.at-rz injected
was three-tenths cf the fuel *.*eip..:t. A1l of tne ooerati:. conii-
timns A' the etnginE an'J oscillosc -ie wi:re th. sa.e io:' t:.L. t'ro runs
of figuree 3 except the v.ater inje,: ion. The an,)litud. of the vibra-
tions rtgisterel on t.l_ qir~nc:s a track? was considered to be indica-
tive ol inci-)lnt k..oc; b-cajsc -. lc'.,er ampli.t'~-ic f vibrations was
not readily 'itect :a v.isulllj 3n t.:. 3ascilloscope. The ".*atcr-fuel
ratio i' 0.3 with iinjactic',. at the :ptimr'.n cri.n- angle consistently
gav2 incipic.it k.ioc'- or n., knock. The i.p waiter-fuel ratio was the
lowest obtainable .Jitrn to *,tetr--injectin syst.-rr; therefore, the
smaLlest wat2r quantity rncessary to quench te Lknock w3ss not deter-
in'eI in tlis i *!vesti;,tiun.

H ;-h-spzsd I.atioo ..icturcs ci the qun.nct'ed combui-tiin of
.i- 5 Lu-l lnr:"cat'. tJhat, tie- '.r.o;. lid in -. 3c ',ur in t:;..t -art of the
end zone iprime-atz.J ly tihe wa-.r, -it that t.-, inci.i-nt Krn.ck such
as rangiter,. on th qj-ncheJ track L. i. l;1,'e 3 came from a v--ry
small fraction of 1.i 3. .al',? l1ouatcl j- ..ith:-er si jo' thI. r-ater
spray nufar t:, cylL :r j.l. if i..;. small *oc"et of' as Inear the
watcr-injecti:r rin.oz- :1l-:.,;5iJ13 .r.C c li: 1 r :1 co.ild have been
spr.r.c-:l 1 .-ith w'*at- i-,. sibh y all tac-s ::,,;c- .,'2.:'- h.ve_ bean
rc novJ.

In. nov'r 1.:.: rslti- fr-" sever- k ic i3 s.un in iir-
lure T. r.L i." t.r-'.ces are neJarly identical :'.3orox.liaitely to the
)Oint "-'hore kri::oir occIrrri in t;L. unqu encha-l tr.-ace. Thi loss of
energy .*viUis ea;vy '.:ock carrot he acrintc i'or as beinF involved

i-ACA R3 No. ELI27

in the energy ol vibration of the gases, because even alter the
vibra..Li-ns have buen nearly SJmo~d out the unquenched pressure-
time tr'Lce remains about tIe sarLe distance bel-:w tli. quenchled
trace. Some af the energy nar, b. inst in tne higr nei iat transfer
through th. cylinder walls with heavy knock "e-cause of thr-: greater
scrubbing action of the gases on th.: chamber walls, as suggested
by Withrow arid RassweiLer (reference 7). The greatest p.:,rtion of
the energy loss might be *Iccourtable in the fonn )1' unreleased
energy in unburn-cd carbon. Durnin, every, vi ,L;int knocking ran mcae
in these tests, the engine releisedI a .larie uantit;y 1f black sn.-ke
on the exhaust stroke. W'ieen thei kn-,c.k was reluce.l to ih? i-ci-ient
lkvel, eiitner by quenchlin or by increasing the anrtiknock value of
the fuel, n' traces of smoke were. nt.e i. I.'a:Cu-l (rcfrence 3)
Lhas presenteJd ;.a-ur--nmets oD ot'.er 1:.s witi, ea'ry kn.ck.

The traces .i' tijo J.'iring cyc-Ls were suerls ri s -i in fiLuvre 1
to siaow that q'-fl Iic.i-:1 i>!-3 C'u l. ,i :1Jce a'S i'rn p.j"-.:r as untiencP.ed
S-3 fuel. The fctkne rAnting. 3f, -.. *, i 3-5, l'.ls, :s ,.bLained
from the A.S. T.... (I..jtor Uct':,i, e:7 at. n1 10..., r'es-C ctively.
The quenched trace i 'i i l.ra- '.4 ias G a..ri ris, ..-. ~ ..irit i ly at t.le
p-init whier: L.oc wo.ul- J oi-cur' in an-unquen'ich.-d c' c.i Thc sudden
rise in prcssire at. that ,..oint' ii ; I !i r.c..:Lc: -.' .' 1- -. uenched
M-i runs. P. .io, i'tires ) tl- 3. rnn.i h:' -e .:o (.Ot sh.o the
characteristic vibra iins in h-. bo u'ie:C1 ,ase "' i.: aCc:il.na"7 kn':"oA.
The trace for unqu--in'hc-d 3-3 fCu' i., ;:1i c L S3,ws a.ut t'e san.e
ar.plitude ni kr'n)cr.inri vibrat io:3 a c.i J s L' t.rciC: 2ii h 3S-,
figure f:'r qu, nc'eiid '-J fu.el.

The traces shown in figures j and L ar, reprI'se'ntitiv'- .).,u more
than 50 traces tanl:cr i under tr!'. same test -,,l t 'on:. Tnre r'-pioduc-
ibility of the test .at.a vI'as very '.:odi; l.urtL;ermore, titc orier "'i
taking the two traces on the car.is vws reverseJ rman;, Limes and
identical results were .-bctaine:i.

The oaUtirim' .:ri ,:l fr start of water iniecL-i-on, with rec-'ect to
knock wvias f"iunl to :-; criticuil; ander r.ne c'*.*l!iti ':ns o the tests,
the optiniur an6l.- was fro.-. j0 t) *')- -;.T.C. o,: t)i- c jr,.,r.ssion
stroke. The t.,t.al time re ire : i-i inecti ..)i o u tei, a.: indicated
by the hiigh-spc: l .i to1 r iOO -hs ..:. ." t.t 1.C .:. f :.'.ra:nk an-le Start
of injection even as late a-s !s'3 B.'.T. .lid .,: .t i'.'- -so 1 r results
regardless of the quantity of water' i nectei up t. th t cap:aity of
the water-injection s./stem, wvhic. i.,. ti. ..es t .- fuel qununtity,
or 12 times the water used at t:w it. L-ir.. .c.'l?. T'-e J rre til:e
lapse b--twPen kn:o- k an; inje..ti.or 5'C" ni .i:.':. n :Le 'i I., not encour-
aging fro:r, LW. cu'si ier.-tion -. ra .. t to t con it ins
:of fli. t. If the .TA riin,., ti,-e I:v-e.--n at.;r i. "..ei ,:, .- I con.-
pletion of hurnin.'- rc.mains cnst.- .' li i' re. t nl,: .i' speeds, the
mtinnumn anrle of injection foi ,- :0o rec.lts ,.ri Ll increase fi'fr 50C' at

NACA R3 No. EI?27

570 rpm to 24L at 2G00 rpm. The problem of injecting water when
the nistcn is near bottom center in such :.anner that it will be
concenitrated in the end zone when the piston is at top center will
be difficult.

With injection of water betw en 600 and 1520 B.T.C., the quan-
tity of vrater req'Lired to ure.-ent t.ie t:i-3 fuel from exceeding the
incipient ~:ock limi t increased luoidly fr'or. U.3 to ;.6 water-fuel
ratio. As the injecti'-i angle was advanced biyoni 1.320' B.T.C. on
the cor.pression strike t 20" A.T.S. on ti'll i nt.a:e str ke, the
knock inte.nitiy :onbinuou.sly inccrcased at .-: constant water-fuel
ratio of 3,.; r.lsn, the ilamie speJ decreased and knock occurred
later in tih c:-cle. Ihe slower ;ate of b-rninC lowered tile cycle
efficiency consiJera.l y. Fr'the. ..'?, soe cycles were drovned
out with the 3.6 watcr-'uel ratio directed at 200 A.T.C. on the
intake stroke.

Injection earlier thai 200 .".T.C. on the intake stroke was
not ncssibcl bccalse of mechanical lir-.it.atin:s. Injection at this
angle was as nearly co21rirable %ith int.ro incinE the coolant into
the ":anifol.i near the intake valve as ,j-ssibl, with the apparatus
used. In fther engines, dependi;-:. on the operating co:iJitioqs,
introducing tie crol3int into tho r,.anifold near tie intake valve
will reqniire different wat.r quantitLes for the seame effective
knock reJuctioi,. 11-e 3. water-fuel rati us'?-1 on ti-is apparatus,
therefore, shole'ild r1. b-u used- in makinr comparisons with o-ther
eng ines.

In order to as,'u.- as thio'.-'uh d minxingr- of the water and the
fue'l-air c!il:-r? as posniole, t!i. lLrin valvts u se3e in the nirns of
figiurs 5 and I'. wvEre re.''laced by lhroi.fpedi valves for tn(. run .-f
figure 5. The shroude'l valves i.cireased the t'rblulence, artic-
ularly Juri'r- t'-e air intake. F- -ir.. 5 is a iressure-time:trace
takln v. jth Mi-3 f el, 3.5 w.ater-f:-l1 ratio:, wat-r injection at
2%_? A.T.C. ori tiie L,.ftfl' 3t]i l:e, 1. J c L 3thCr zo iitions the same
as for the oth.-r rui,.. The Ioi.:c'- i.t -n3ity :.r" :'i.t r'ed'ce.i appre-
ciablr front, that proiel.ce'l byv *-n'uei'jeic. -j ft1''l, as Siwn in fig-
ure 3. ,- raLt 3: ..essu'e rise ari. ctr..b.lstion wv. a a-preciably
reduced as conr'T'iar w..th tn.- -.~ c-s-nrc ':.se it t h,-' o.-tiJ.urm. injection
anile (figs. 3 n'l 1a.), nartic'. :rlyi i!rl:-a" cr 'lier stares of
co .bu. -t.i;n. ,;-.th .;- :; 'i-o IJ al .-- tir- -. .. r--s-u'we rise was
c'-isi:lcrably g' : .ter .- t.in -.;i t: r ;. 1 v lv's at t,-' earliest injec-
t.i.n anole a'l the largest 4uant '.* oi -vatir.

NACA RB No. Ehl27


The following results w'.re ootiinad from limited water-injection
tests c'ndact.d on the I]ACA combustion a,:.naratus at an engine ooer-
ating speed of 570 rpm:

1. Injecting water into the end zone with a vrater-fuel ratio
of 0.5 reduced the knock intensit- of l.i-5 f'ul to that .-I' S-3 fuel
without vjater.

2. The considerable power In's associat-d witr violent k; ock
was prevented in the cyicles in wt :.ci t'-e knock '-as quenched by
end-zone water injection.

5. Tihe tntimun .njele of water injection was critica..

Aircraft Engine Research Laboratorv,
National Advis'wry Comnnittee 'or Aeronautics,
Cleveland, 'lio.


1. Miller, Cearcy D.: A Study by 'lirn-Snee'I Phot.o:ra',ly if Co:.bus-
tion and Knock in a Luark.-linit in ErEngine. 'JACA Re-. ]Jr. 727,

2. Hopkinson, Bertrar.: A :ew lIet.io oi' Colji.,- Gas-Engines. Inst.
n:ech. Eng. (Prj.), PL3. 54, Jull., 11), 0.). '79-l15.

3. Clerk, Du'alJ: Cylinder Actions in Ga.;, Ln:i Gasoline Enit.ires.
SAE J.ur., vol. VIII, no. 6, J,'ne 1921, rp. 2;;-539.

14. Rothrock, Addison i., Krsek, ilois, Jr., arid Jones, Anthony l'.:
Summary Re-ort on the Ind'ict oni i' Watcer to tie inlct Air as
a Means of Int':inal CoolL:' i Ajircr.-it .n.Y ,ne Cyli.iderri.
NACA i.R, Auc. f1942.

5. Kikring, L. S.: ..ater -ind Wat r-Ak'cnhol Injerctinn in a Saper-
charged Jai-iAr ircraitL 9fi inC. Canadian Jou'. lRc.r, sec. A,
vol. 16, Air. L. i, .p. ..'-1.7? .

6. Rothrock, A. !., and Sprencer, C.: A P-:toFrd-!-Ac Study of
Con:hustion and Knock i.n a S.ar''-Irnitio.l En; _rn. ? ACA
Rep. '4o. 622, lI.8.

8 NiAGA. RB No. Eli27

7. Withrow, Lloyd, and Rassreiler, Gerald 1.: Slov hintion Siows
Klocking and Nnn-Kn.:'lin,_ Ex-losimns. SAE Jon*'., vl. ,9,
n 2. 2, Aug. 19"7, --. 29 7-05, 312.

'3. YiacCull, leil: Power Loss Accoripanyinr Detonation.
vol. L.i, no. i, .,ril 12?9, -i.. i.t- 60.

SAE Jour.,





Outline of

/ sLate
I spark plug


Water spray,-

spark plug--


J--Woter-Inject on nozzle

Figure 1. Photograph of water spray in combustion chamber
after water Injection was complete. Combustion
has not taken place. Exposure time,
25 microseconds.

ACA RB No. E4127

spark pi

Fig. I

pickup-7 ,

SFuel-Inject on
' nozzle-

:, ;. II


.:E ..



Fig. 2

RB No. E4127
s pa rk

pickup-7 \.

I,/- --Outline of
/ combustion
/ chamber

/ Area that has been
I traversed by flame

I/ spark plu I outline-
\ l 1




I ,- r m
j End zone
\-Woater-Inject on



Figure 2. Location and shape of end zone a few engine
crank-angle degrees before completion of burning.
Exposure time, 25 microseconds; relatuie position
of water spray, shown by dotted lines, was
obtained from figure 1.


NACA RB No. E4127 Fig. 3


>< e
3Z 5 .

00* ,-. b

0 gJk
|< a
O a aI

Ii. 0 0.lb


It aDI

o a Lb
/ U' t0 0

in 4a a.

Ir I ^ 2
-^. "*tt **
^^. i 0*
"s^ ~ ~ 9 I4 k
>. l~ ^ f
^\ *;*-
^ s:^P
O -^ 0 *
^ nr .
i I fc .0
| ~~teo

NACA RB No. E4127 Fig. 4


-o IP
cn O 4 w,

qa 9 ao
-: 0 4- a

it I .OO
41- h- I0
Z- b

f 0 0 |

b% 46

f 0IaI

o *
rr\ o o h

1, "< \ b .

: \ ti
L; bb..

aD~ )
f. .S

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z -



L o


-0 Is.


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I3 4.



w0 ,L
S** *.
0 .te



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I 0&
0 0
L -



Fig. 5






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3 126 8 095
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