plastic 2 dimensional rocket engine for testing solid propellants

8/10/2019 Plastic 2 Dimensional Rocket Engine for Testing Solid Propellants

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REPORT 4

PHOTOGRAPHIC INVESTIGATION OF COMBUSTION IN A TWO-DIMENSIONAL

TRANSPARENT ROCKET ENGINE 1

By DONALDR. BE LLMAN,ACKC. HU MPERE Y,nd THEODOEEIALE

~

SUMMARY

il~otion p i ct u r e-sa t camera 8peed8up to 3000

fr m s p r

second t oer e t ak en of t h e combu st i on of k i gu i d oxygen and a

hyd roca rbon fuel i n a t r ansparen t -si ded rocket engi ne. Th i s

100-pou nd -t hr w st en gi ne ct it ed bt ial ly of m ei aJ con tou r

and i n j eci%n p l ates cl amped between two p l ast i c shed8. T %8

de@n provided an es8et i ia .Uytwod


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. . .

.

600

REP ORT 1134NATIO,NU ADVISORY COMMJ .TTE FORAERONAUTICS

.

- -

Goseoiisaxygen-gasolirm \ ~ .- Pressure ,:-Spmer

flumeigniter---- : , ;

top ,, r blocks

:- Clomping

L-

~j~ ~

.- ~ t ~ r

L-Transparent

I

1

plo e

plate sheet

1

.- -.. .-.

La I-- .. _ ~

r

7

I

I

L.

(b]. . -. -._i

(a ) View of

unassembledengineshowing tra nepaxentnozzle contour

ata equipped with singleimpinging jets .

(b ) Vi ew of a s se mb le d en g in e s how i ng t r a n spm e

n t n oz zl e con t ou r

ate equipped with singleimpinging jets .

(o) C u t a w a y v ie w of e ng in e w i t h d id -copp er n oz zl e a n d e qu ipp ed

lfi-para llel-jet injector.

FIG URD.Tra nsparentr sidedrocket engine.

com bu st ion pr es su re t a p a n d a pr es su re vibr a tion picku p

r e in st a lled t hr ou gh on e of t he con tou r pla t es a t a bou t t he

poi nt of t h e com b us t ion ch a m b er .

Th e eig ht i nject or s a r e d ia g r a mm a t ica l ly a h ow n in fig ur es

a n d 3. Th es e m a ybe cls sa ed a s im pin gin g jet s, im pin gin g

jet s w it h t ur bu len ce pr oject ion s, a n d pa r a llel jet s (s how

hea d). The pr opella nt s w ere ignit ed eit h er by a ga se

oxygen -a lcoh ol fla m e, w hich in t ur n w a a ign it ed by a sp

plug, or by a gunpow der sq uib w hich TWX+ired in t o

cha mber. I ?or runs 1 t o 12, t he ignit er w a s loca ted a t

cent er of t he inject or ; for runs 13 t o 15, t he ignit er

mount ed perpendicula r t o t he m ot or nxis a nd 2% inc

d ow n s t r ea m of t h e i nject or .

P r opella n t s ys tem s.-A s ch em a t ic d ia g ra m of t he pr o

la nt sy st em used t it ht he first engine inrun slt o12is

show n in figure 4. The ga solin e t ank II w a s pressur ize

20 pou nd s per sq ua r e in ch by n it rog en fr om r eg ula t or F

or der t o

m in im ize ca vit at ion in t he in let t o t he pum

F rom t he t a nk, t he ga solin e flow ed t hr ough r ot a met er O

t w o, f ou r -cy li nd er , p ot i ti ve-d is pl a cem en t pu m ps D D , w h

w ere &upled t o a single m ot or E E . The eight pum p

st rokes w ere unifor mly st aggered t o produce a minim

flow v a ria t ion . F r om t h e p um p, t h e g s soli ne pa a s ed t h ro

a s er ies of h yd ra u lic r es is t rm ces B B t o eli min a t e pu ls a t i

Th e g a sol in e t h en flow ed eit h er t h rou gh pr opell a nt con

va lve Z snd int o com bust ion cha mber V or t hrough r e

va lve C C a nd ba ck in t o t he supply t a nk. D uring a run

pr es su re of &bou t 400 pou nd s per s qu a re in ch w a s r eq u

t o s en d t he fuel in to t he com bu st ion ch a mber , a n d t he r e

va lve w a s set a t

a

pr es su re of 900 pou nd s per s qu a re in ch

t ha t n o fuel w ss bypssa ed w hen pr opella n t con tr ol va lv

W-M open.

a

oxygen

/

KO

>31XI

m en t of a n on lum in ous pocket . Wit h t he use of t his va lue,

t oget her w it h m ea sur ed va lues for com bust ion -ch am ber

pr essur e, w eigh t flow , a nd a rea in a ccor da nce w it h t he fol-

low i ng eq uu tion , t h e r a t io of t h e com bu st ion t em per a t ur e t o

t he m olecula r w eigh t of t he pr odu ct s

TJ m can

be deter-

mined:

T ._ VoPcA c

% WR

1

where

T.

combust ion-chamber temperat ure

m

~verrigemolecula r w eight of combust ion ga ses

v

gas

el oci t y i n com bu st ion ch a m ber

P.

combustion-chamber pressure

A. combust ion-cham ber cross--sectionala rea

W

t ot a l p rop el la n t w e ig h t f low

R

u n iv er s a l g a s con s t r m t

In m ost of t hese exper im en ts, t he cr oss -sect ion a l a rea a n d

t he. combust ion-ch amber pressure con tinua lly ch anged a nd

t here w as inst icient t iming correla tion t o det ermin e va lues

for t he pressur e a nd t he a rea a t t h e exa ct t ime for w hich t he

velocit y w a s mea sured. Th ese mea surement uncert ain ties

a llow only a n a pproxima te mea surement of

TJm

by t he

use of eq ua t ion (1). Th e r a tio T Jm can be d et e r min ed h or n

ot h er m ea s u re d q u a n t it ies ; t h us

where

A,

n ozzle-t hroa t a rea .

ill combust ion -cha mber ~ la ch number

Y

ra t io of specific h ea t s

9

a cceler at ion du e t o gr avit y

E q ua tion (2) ca n be derived from B ernoullis eq ua tion by

a ssumin g a n isen t ropic process. Th e ra tio of specific hea ts

ca n not be experiment a lly mea sured, but t he use of t h e

t heoret ica l va lue of t h e ra tio of specific hea ts in t r odu

only a sma ll error .

F or most rocket engines, t he effec

combust ion -ch a mber N1a ch n um ber is so sma ll t h a t it

be neglect ed. I n t he first 12 experiment s report ed,

n ozzle-t h roa t a rea va ried grea tly during t h e runs, a nd

seq uent ly t he use of eq ua tion (2) t o det ermin e

T Jm i s

s ub ject t o m ea s u rem en t u ncer t a i nt ies :- Th e-f ol low i ng t

pr esen ts t he r a tio of t he m ea sur ed va lues of

TJm

a s d e

m in ed by t he use of eq ua t ion s (1) a nd (2) t o t he t heor e

.

. .

va lues of

TJm: -

Run

hje 3r system

I

heo-

retical

T.-/m

Ii

I

5

Mnltlple fnterbwtfng Jets wftbont tnrbnlenea

Prom ------------------------------------

254

k

1I TWO@a ofi ntemetf ngj etsf tbSPLAI pMes--

a?.a

15 I 16~dj t i - - - - - -- - - - - -- - - - - - -- - - - - -- - - - - -- - -

87

16I 31PereUelJet i - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

57

? awnd Tr

Theoretfml T

m

qn tfon Eqna

a46

I

0

a n a

.

a m a

Th e a r ea s used for t he va lues sh ow n in t he t a ble w er e t

for t he s ta r t of t he r un for t he t ra n spa r en t n ozz le (r un s 4

10). Ot her va lues used -w ere t a ken a t t he m a xim

combust ion-chamber pressure.

D uring ea ch run w it h

t r a n spa r e nt n oz zle, t h e n oz zl e-t h r oa t a r ea ch a n ged b y a f a

of 2; h en ce t h e m ea s ur em en t u ncer t a in t ies for t h e va r ia

of eq ua t ion (1) w er e pr oba bly less t ha n t hose for eq ua

(2). B y t he use of eq ua tion (l), t he r esult s show t ha t

measured

TJm var i es

from

a bout 40 t o a bout 70 p ercen

t h e t h e or et i ca l

TJm.

IRREGULAR COMBUSTION PHENOMENA

STARTING CHARA(XERISTICS

S om e s t a rt s w e re s moot h ; t h a t i s, t h e com bu st ion s pr ea

a st ea dy m an na t hr ough out t he cha m ber . Ot her r un s w

er ra t ic; a t t he st a rt of t hese r un s, a sm a ll fla m e a ppea re

t he vicin it y of t he in ter sect ion of t he pr opella n t jet s.

fla m e s w el led a n d d im in is hed i n a n ir reg ula r a n d ~ e ven m

ner during t he t im e it w as ext ending t o ~ t he com bus

chamber.

In ma ny runs, a bout X second w a s req uired

t h e fla m e t o f il l t h e en t ir e ch a m ber a n d t o b ecom e r ela t i

stable.

S om e t im es t he s ta r t con sis ted of a s er ies of ex

s ion s, a s s how n by t h e s eq uen ce of ph ot og ra ph s in f ig ur e

E xplos iv e s t i zr t sr eq uen t ly ca u sed b ur st @ of t h e w i nd

t his sa m e ph en om en on cou ld d a ma ge m et a l ch a mb er s.

EXPLOSIONS

S t a r tin g expl os ion s ca n exi st in a m il d for m, a s il lu st r

in fig ur e 16, or a s m or e d is a st rou s s ta r t s, w h ich a r e d iff

t o r ecor d a nd t o eva lua t e. I n figur e 16 t he bur nin g a pp

t o be n or ma lly sm oot h d ur in g t he fir st cy cle, w h ich pea k

t ie 5. H ow -ever , t he burning in t he second a nd t

cy cles; w hich pea k a t fr a mes 27 a nd 51, r espect ively ,

explos ive. Th e s pa t ia l lu min os it y ch a nge bet w een fr a

25 a n d 26 is fa s t er t h a n t h e m ovem en t of pr opell a nt s t hr o

t he sa m e spa ce (n or ma lly in t he r a ng e of 100 t o 300 ft /s

Th er ef or ej i t s eem s r ea s on a ble t o con ch de t h a t a n u nbu r

mixt ure w a s condit ioned t o become explosive a nd

s om e un recor ded d ist ur ba n ces t rig ger ed t he com bu s


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608

REP ORT 1134NATIONAL ADVISORY COMMJ ITE

FOR AERONAUTICS

C-33060

F m u r m16.-Starting explosions of liq uid ox yg en a n d w olin e in t r a ns -

p a ren bs id ed r ock et en gin e w it h m ult iple in t er sect in g jet s w it h

t u rb ul en ce p roject i on s . Run 8; ca mera speed a t fra me 1, 602

frama p er se con d ; cam e r asp e ed a t f kam e 60, 695f r am e sp er sec on d .

a lmost simult aneously t h roughout a ll pa rt s of t h e cha mber

or t r iggered t h e mixt ure by a w ave compression.

bot h er seq uenm in w hich t he st a rt w as explosive is sh ow n

in figure 9, fra mes 1 t o 6.

S iice only t h e ignit Or fla me a p-

pea rs in fra me 3 a nd t h e en t ire cha mber is luminous by fra me

5, n o upper limit of spa tia l velocit y ca n be. comput ed; but a

fla me velocit y of a bout 500 feet per secon d or grea ter is indi-

ca ted beca use t he fla me ills t h e first 7 inch es of t he ch a mber

of fra me 4.

~ losion s from previously ment ion ed improper mixing

ma y occur during t h e middle of a w a s sh ow n by figure 12.

P roject ion of t h e seq uen ce sh ow ed t h a t t h e st a rt w as cyclic

bu t

t ha t s moot h s tr ea m in g com bu st ion exist ed by t he t it

fr a me of fig ur e 12.

F our d ar k a rea s, A in fr am e 1, pr oject

i nt o t h e ch a m ber a r ea a n d p ul sa t e l on gi t ud in a l ly , s om et i me s

becom in g q uit e s ma ll a n d ot her t im es q uit e ext en sive. On e

or bot h of t he t op d a rk a r ea s in dica t e m a h%n ct ion in g of t he

in je ct or , a s e vid en cd d

by prope~~t circ~ation fi th~t area

a nd show n by B in fra me 4.

M om en t my m a lf un ct ion m a y

or ma y not be serious;

for exa mple, a slug of a ppa rent ly

u n bu r n ed p r op el la n t p a s se d h a r m les s ly t h r ou g h t h e ch a m ber

(in dica t ed in fr a me 2 of fig . 12 by C ).

S oon a ft er wa rds a not her slug of un bur ned pr opella nt

st ar ted t hrough t he cha mber a s show n, for exa mple, by D

in fr a mes 29 a n d 43, bu t t his s lu g explod ed w h en it r ea ch ed

posit ion E in fra me 48.

Appa r en tly , t he s econ d s lu g h a d

s n. flicien t ig nit ion d ela y t o b ecom e ex plos iv e. Th e com bu st i

mecha nism or ra te a ppea red t o be cha nged, a s eviden ced

t he in crea sed lumin osit y. Th e in ject or flow ma dist urbed

t h e w q d os ion

but q uickly reest a blish ed it self (fra mes

t o 63); combust ion ra pidly follow ed t h e reest a blishment

t he inject or flow , t h e explosion ga ses w ere sw ept from

ch a mber , a n d t h e syst em a ppea r ed t o be n orma l by fr a

84, except for occa sion a l slugs of unburn ed propella nt t

d id n ot explode (t ypica l of t ha t sh ow n by F in fra me 7

Th e seq uence sh ow @ t he midrn n explosion in dica t es

condit ion ,t ha t a lso ma y ca use dest ruct ive da ma ge t o en gin

F rom t he phot ogra ph s it a ppea rw t h a t t h e va r ia t ion

ignit ion la g from improper mixing in dica te9 a propella

mixt ure ra t io t h a t ca n ca use st a rt ing explosion s, midr

explos ion s, a n d ot her t ra n sien t ph en om en a .

COMSU WONOSCI LLA~ONS

J -xxv-freq uency oscilla t ion s, commonly know n a s chu

gin g, a re illust ra t ed in t h e seq uen ce of figure 17. T

ph en om en on of ch ugg~ ~ w a s iir st en cou nt er ed a n d per ceiv

t hr ou gh t he t ech niq ue of t ra n spa ren t ch am ber ph ot ogr aph

F igure 17 sh ow s 2% cycles of chugging w it h a freq uency

a pproxima tely 98 cycles per second. Anot her sequence,

F m w r in 17. L ow -f req u en cy os cil la t i on or

f req u en cy , 98 O YC I Mp er s eoon d ; ca m er a

secon d.

.

ch ug gin g. C h ug

s pe ed , 1600 f r a r ncs


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COMBU SmONIN A TWO-DIM33NSIONALTRANSP ARENTROCKETE NGI NE

illust ra ted, w a s a na lyzed a nd found t o give a frequency of

103 cy cles per s econ d. C h ug gin g i s ch a r a ct er iz ed b y a r m t ed

flow w it hin t he cha mber a nd som et im es by flow rever sa l.

An a l ys is of pr opel la n t f low s a n d ch a m b er com b us t ion pa r a m -

et er s (r ef. 4) h a s r ev ea l ed a log iq a l expla n a t ion of ch ug gin g.

Th e a n a ly sis s how s ch ug gin g t o b ea n ou hof-ph a se cou pl in g

bet w een t he flu id flow of t he pr opella n t feed s ys tem a n d t he

com bu st ion pr oces s in t h e r ock et ch a m ber . L ow pr opelk mt

pr es su r e d r op a c ros s t h e i nject or a g g ra v a t es ch ug gi ng , w h i ch

usua lly ca n be a llevia ted by use of a n inject or design t ha t

incor pora tes t he use of higher pressur e drop. D uring t he

st a rt of m an y of t he r un s, a dist in ct oscilla t ion of 100 t o 300

cy cles per s econ d exist ed . Th is os cilla t ion cm w pon ded t o

a br igh ten in g a n d d im min g t hr ou gh ou t t he en tir e com bu s-

t ion ch a mber , a s illu st ra t ed in &m e 14.

H i gh -f req u en cy os ci ll a t ion s h a ve a l so b een en cou n ter ed .

When

T+n i s know-n,

com put a tion of t he speed of soun d

t h rou gh t h e com bu st ion g a ses a n d t h us of t h e v a r iou s n a t ur a l

fr eq uen cies of t he ch a mber is pos sible. B y u se of a n a ver a ge

v a lu e of

TJm

a s obt a ined by mea ns of eq ua tion (1) a nd a

t h eor et ica l va l ue for t h e r a t io of s pecif ic h ea t s , t h e f ollow i ng

va lues w er e d et er min ed for t he n at ur al fr eq uen cies

combust ion chamber:

C-33062

F m U B E17Concluded. Low-frequency oscil la t ions or %hugging.

C hu gg in g f req uen oy , 98 oy olea per s econ d; ca m er a s peed , 1500

framcaper second.

Length ----------

m

Width ..-.. ----------

TtdoknEss-----------

Qam

I n t h e com bu st ion -ch a m ber -p r es s ur e os ci ll a t ion r e cor

vib ra t ion fr eq uen cies w er e pr om in en t t hr ou gh ou t t h

on e a t a ppr oxim a tely 1900 cy cles per s econ d a n d t h

a t a ppr oxim a tely 25,000 cy cles per s econ d. Th ese

t ion s, t her efor e, a ppr oxim a tely cor res pon d t o t he

fr eq uen cies for t he len gt h a nd t l+ ickn ess of t he ch

S a m pl es of t h e v a riou s os ci ll a t ion r ecor ds h e s how n i

18. O cca s iom d ly a f req u en cy of a b ou t 4000 cy cl es per

w a s r ecor ded , ~ d &is fr eq uen cy w a s foun d t o be t he

fr eq uen cy of t h e t h ru st s ta n d.

SU M M AR Y O F R E SU L TS

A

t ech niq ue w a s developed t ha t used h ig h-speed , m

pict ure phot ogra phy t o st udy combust ion in

a

100

t h ru st , t r a ns pa r en t -s id ed , t w o-d im en sion a l r ock et

O~ g en a n d eit her g a solin e or h ept a ne w er e in tr od uc

t he cha mber ,t hrough a va riet y of inject or s, a nd

pict ur es of t he>bu rn in g pr oces s a lon g w it h s im ul

r ecor din gs of oper a tion a l a n d os cilla t or y d a ta w er e


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RE P ORT 1134NATTONALADVISOR Y CO

MMIMDE FOR AERONAUTICS

f ol io w in g r e su lt s w e r e obt a in ed :

. Al l t h e i nject cn s s hoy ed n on ur lif or m i~ of com bu st ion .

. Tu r bu le nce p r oje ct ion s u s ed w i t h t h e in je ct o rs in cr ea s e d

a p pa r en t m ixi ng a n d ci rcu la t i on of p rop el la n t s .

. An in cr ea se in t he n um ber of h oles of t he pa r allel-jet

ct or s t en d ed t o i ncr ea s e t h e u n if or m it y of com bu st i on .

. P l a st ic-w i nd ow pa t t er n s pr ov id ed a d d it ion a l in for ma -

r eg a rd in g g a s-f low pa t h s a n d q ua l it a t iv e in dica t ion s of

temperatur e varia t ions.

. Th e r a t io of t he com bu st ion t em per a tu re t o t he m olec-

w eig ht of t he pr od uct s, ca lcu la t ed fr om ga s velocit ies

a i ned fr om t h e com bu st ion ph ot og ra ph s, w a s com pu ted

e 40 t o 70 per cen t of t he t heor et ica l va lu e.

. Va r ia t ion of ig nit ion d ela y fr om im pr oper m ixin g in di -

es a propella nt m ixt ur e r a t io t ha t ca n ca use st ar t ing

losion s, m id ru n explos ion s, a n d ot her sh or t-d ur a tion

i en t ph en om en a .

. L ow -f req u en cy os ci ll a t ion s of a p pr ox im a t e ly 100 cy cl &

second w ere recorded during som e runs. S om e of t he

t s g a ve fr eq uen cies of 100 t o 300 cy cles per s econ d.

C om bu st ion -ch a m ber os ci ll a t ion s w er e r ecor ded t h a t

a pproxima tely corr esponded t o t he resona nt fr~ q uenciea of

t he lengt h a nd t hiclmw of t he combust ion cha mber.

Lmvrs I?LIGHT PROPULSIONLABORATORY,

l VATIO NALAD v is oRY C o a fa r r r rm F O R&3RO NAUTIC S,

C L E VE L AN D ,O H IO , ~ a ~ %??,196 .

REF EREN C ES

1. Alt eeim er , J o hn H .: P h ot og ra ph ic Tech niq ues Applled t o C om

bu st i on St u dies-Two -D i men s ion a l Tra n s pa ren t Th ru st C h a m

ber. J our. Am . Rocket S ot ., vol. 22, no. 2, Ma r.-Apr . 1952

pp. 86-91.

2. B er ma n , K ur t, a n d L og an , S t an ley E .: C om bu st ion S t ud ies w it h

a Roa ket Mot or H a ving a F ull-h ngt h Obser va tion Window

J ou r . Am. Rock et WC . ,v ol . 2 2, n c. 2, M a r . -Ap r . 1962,p p. 78-86.

3. B er ma n , K ur t, a n d C hen ey , S a muel H ., J r .: C om bu st ion S t ud ie

in Rocket Mot ors. J our. Am. Rocket S cm., vol. 23, no, 2

Mar.-Apr. 1953, pp. 89-95; discussion,pp. 96-98.

4. Tia ch ler , Ad el be rt O ., a n d B e ll ma n , D on a ld R .: C om bu st i on I n st a

bil ity in an Aoid-Heptane Rooket with a Prcasurized-ChsI%orM

la nt - P um pixig S yst im .

N AC A R M E 51G 11.)

N AC A TN 2936, 1953. (S u per si do

{

.

.

plastic 2 dimensional rocket engine for testing solid propellants

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