Faldetta, Richard D

Holms, Authur G

English

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NATIONAL ADVISORY COMMITTEE 
FOR AERONAUTICS 
TECHNICAL 'OTE 
No. 1116 
STRAIN -GAGE STUDY OF INTERNALLY COOLED EXHAUST VALVES 
HAVING VARIOUS THROAT DESIGNS 
By Arthur G. Holms and Richard D. Faldetta 
Aircraft Engine Research Laboratory 
Cleveland, Ohio 
Washington 
August 1946 
https://ntrs.nasa.gov/search.jsp?R=19930081821 2020-06-17T22:50:44+00:00Z

J;Y~": .LOl'JJ:L J8VISORY COW>tITT.,:,E FOR Am NAUTI CS 
TEC1llaCA:, FOTE NO . 1116 
STRAll'l"- G ... GE S1'lJDY OF l"NTEPlIJ.AJ,LY COOLED EXHAUST -Vlu .. ""?;'S 
HAVl...JITG VjillIOUS THROAT DESI G:LJS 
By Al~th lr G_ Ro:L..~s and Richa~d D. Fa1detta 
SUMMARY 
Three illte::!.'nal~_ji cooJed exhaust valves having the sarrre ex-
ter nal dim.e:1s~ ons -bU-C ~lifferGni::, thrQat designs vTe- e i nv0stigated 
to determine a met:lOcL of obtainin increased coolant - flm. area 
vithout increasing 8tre~s~s . T'lle valves ,rere staticallj' l'::>adod 
to simulate stresses in the t hroa t r egi,)l1 caused by val V'J eJ_osure . 
':'ests sh0,,:red that a co .!.ot_'ic-G:!.on in the co::>J.a t - f lOi" pa sa e can 
be removed w,;,thout increasing strasses . Such an inel~ease :i::l the 
cc>::>lant - fl .... r area l ouers t~'e crOV21 te!!lperat'-~re . 
A combin,eti')n of exeessi ve operating stresses anJ. temperatL;res 
causos exhaust v1.1ves to fa1.1 at t~1e ero ffi . '!:'he ir.)ortance of 
valve tomperature mOld resul tins ty~os of failure are yrcs0::lted 
in :~efe:r'€)::lce 1 . Hear·ul'emGr..ts 0: crown o-poratin.> tGl._peratuyes are 
discussed in reference 2) ,·,hich 8hm'fs tha-~ the crmffi temperature 
can be ::~€)d\lce rl 1)y increasinG the co-:.'la~lt-f10H m:-ea . tn increase 
Jf t:1e cooIant- i': .. 01' al'ea in the region of tlle Jc:1T".:·nt necess i tates 
a re 'uctioTl ir:. the c:coss - sec-:'~;Jnal area of the V2.1 ve stom at 
t:~ig lQcB_tion; 8"ch a reduction would ordinarily be thought to 
il. crease -;,:1e l'l3.XL".:Ul'l stYe-ses . Val ves have beeCl knO,ll:l to fa i1 
at the t~'1r0a-G and exaDples of such f::tilures are deser Ibed in 
ref·3rences :..; 'mel 4:. :it wo'-lc_ be desi~a. 1e to e::l1arge the coolant-
fJ_Oil area .... ll t>Ol1t i!1crea 1n[:; the stro3ses in th.s region . 
Strain- gace tests to c0hl-pa:.~e t:1e "'train- ~ist:;,'itlltion chara_,ter -
isties of throe eX:lat:st va:" ves '1avins t:le sa;n.e extet'nal contours 
in the 1'eGi-:-.n (,f tre throat were conducted at the NACA Clovel and 
laborat'Jry . One of 'ch'3 test. valves l".au a relatively small 
coolant-f'loH areo. J wiwreas the a-thel two had larger coolar,t - flow 
81'ea3 . T~e 8t:'ain di.s-:'rin~tions for the tr..rec valves '\-lero compared 

NACA TN No. lllG 
for an axial tensile loe.d of 1000 pounds . T~lis comparison is 
indicative of the relative operating stresses in the throats durtng 
closure when the inertia forces of the steI".lS induce tensile stresses 
in the throat regions . 
APPAP.ATlTS AND TEST PROCEDURE 
The apparatus sho"m in figure 1 w'as used in cOlljlh'1ction with 
a tensile testtng machine to apply tensile load to the valves . 
An initial load of 50 pounds \vas used to seat the parts and the 
incre~ent of strain resulting from n 1000- pound increment of load 
was measured . The strains were m.easured with wire resistance 
stra~_n gages having a strain sensi ti ve element of one - sixteenth 
by one - sixteenth ir..ch . Bakelite cement BC- 6035 vas used as the 
bonding agent . The gage were L)cated on the valve as tllustrated 
in figure 2, which shows the gages oriented to meaSl!re the 10DGi-
tudinal strain, that is , the surfaco strain in the direction of 
the longitudinal aX1S . On the first t"ro valves tested , gages were 
also oriented to measure the st;rface stain in a circumferential 
direct:'on . Gages at poL.ts ,.,here the strains should be the same (on 
oppostte sides of the valve , for example) Showed a max"imuDl devia-
tion froin the mean of 8 . 4 per cen't, . '1'he average of mean deviations 
for nine such instances ,.,as 2 . 5 percent . 
The cross sections of the three valves tested (designated A, 
B, and C) are 8ho~ to scale in figure 3 . The internal contours 
were determined from X- ray photOGraphs of the valves, with the 
exception of the dotted portj,ons, 1·,hich were obtained from drawings . 
The s~ecial features of each tr~oat are given in the following 
table : 
Valve Figure Description of trroat 
A 3(a) Tapered bore in stem with sharply 
constricted coolant - flow area 
B 3(b) ~e as valve A except coolant -
C 3(c) 
flow area in tho constricted 
region is enlarged by drilling 
Sa~e external dimensions and 
bor e as valve :B but with heavier 
section between throat and 
seating surface 
2 

RES1.;""LTS AHD DISCUSSION 
In the diagrams of f igur e 3 t:te strain- gage measur ements ar e 
p18tteri in. a di:i:'8c-cion normal to the ' exterior ol1tlinu of the val V8 
from points at 'I-,hi CJ1 the strain gag(')s wero J.ccated . The e.xterior 
:.>Utline of the valve is the zero or datum l ine for the or dinates . 
Curves of Cil~GUT .. lf6renttal strain for val vos A and B (figs . 3 (a ) 
and (b) , respect1veJ.y) sho",T that the variation of the circumf 8r-
en-c'i.al strain in th0 c" 1 tical throa.t r ee;ion is insignifi cant . 
Valvo A (fig . 3 (a)) has a peak of longitudinal strain i n the 
reS'L on a-c . Valve B (fig . 3(b )) has no such strain peak . Figur e 4 
ii:3 a reetanGular cO(" rdj"nate plot of strain against distance aLms 
the valve exte:n1al cont'Jur frLm point d (fig. 3(a)) aI' tlle s eating 
sGrface anC'.. shows that valves B and C ha -"e smcot}:zr strain curves 
in the region of the t:lroat than valvo A. T:t,e te 18ile l':)ud would 
have a tendency to yeduce the curvature of the fillet in the 
region a - c (fig . 3(a)) uith a corresponding tendency :::'or high 
tensile strain in this ::,'egion . T~_e constl' j,c~Gion '~n the :region b - c 
of valve A is believed to pr':)(lUCe considerabLe stiffness in this 
region and thlOs -Co cOY',rine tile deforr.\ation to tl:8 regio:1 a-o . I2:ence, 
the constr';'cti on at b is cO) sidereC: to be the rause ~f the longi -
tudinal str"'ill 2ea~{ bet,l·re8_" ... c,nd b . Valves Band C ).ack selch 
a sharp peak) "'hich :'s attrib",te,: to the a'b", '.mce of tne l·:')cal stiff -
ness (constrictL:m) that Has present in val-Ie A. The c':>82.an"c-flow 
area for valves J3 and. C i'3 four ti:ues i.~r.'lt 0f valve A. E:xam~nation 
of f 5.gure 4 SllO'YiS that this il1Cl'ease Ioras ~')btained '\d th low'er peak 
stresses in the t~!.roat :region, 
COITCLul)ING RE'WuUG3 
A constricti8E in the valve th:roat that redt~ces the cool ant -
flow area ~las been ah01ffi to i1 crease val ve-c~:ovm temperature . 
3 

NACA TN No . 1116 
The se steady- l oad tOGts have sho'l·:Tl. that such a constr l ction can 
be rema"feLt 'l-riti l·.:m t increaslng peak strGsses . The opt imt<m design of 
tLe threat regio~1. i3 conside:ced to be one having no constrict i on. 
Aircraft Engine ~esearch Labaratr.:ry, 
national Advis-:lry Comni ttee f o:;:' Aeronau'tj CS , 
Clevela::ld, 0~1l0 , A!.ll'il 30, 1946 . 
REFERENCES 
}_ . San:iel~s , IT. C. , Mulcahy, B. A. ) and Peters , M. D.: Some Factors 
.Aff e cting FaUnres of Exhaust Valves in an Air - Cooled Cylinder . 
NACA ARR i.-To . 4_11.9) 1944 . 
2 . Mulcahy, B. A. , ar~d Zipkin , M. A.: Tests of Improvements in 
~xaaust-Valvo Performance R(-':sul t:LnG frc,,",- C~anges i n :l:.:Jc1.at,st -
Val ve and Port Des ign . NACA AIm No . E5G26 , 1945 . 
3 . Young , VinC0!1t C.: Aircraf t - Engine Val VG l\lechani S1nS . SAE Jour ., 
Vol. 44, He . :3, ,-~3.rch 1935, :)p . lOS - 1:'...6 . 
4 . Colwell, A. T . : Hcdern Ail'cy ft ValYes, SAE J OUY . , vol. 46, 
no . 4, AP1'il 1940 , PP . 14-,' - 165 . 
4 

N A C A TN No. I I 16 
Cup 
Valve 
Fig. 
Centering 
sc rew 
NATIONAL ADVISORY 
COMMITTEE FOR AERONAUTICS 
Disk 
Figure I. Apparatus for subjecting valve to tensi Ie load. 
I 
. I 
L 
N AC A TN NO. I I I 6 Fig. 2 
'" x ..L" 
16 16 
strain gage 
o 
t 
INCH 
NACA 
C·9315 
3· 20· 45 
Figure 2. - Arrangement of strain gages on test valve. 
· I 
1--' 
I \ 
I \ 
I \ 
I \ 
I \ 
I \ 
I \ 
\ 
\ 
\ 
(a) Valve A. 
\ 
\ , 
, 
c 
Strain 
o Longitudinal 
o Circumferential 
NATIONAL ADVISORY 
COMMITTEE FOR AERONAUTICS 
Figure 3. - Cross-sectional view of test valves. Space scale, three times full size; strain 
scale, 1 inch represents 200 microinches per inch for 1000-pound tensile load. Tensile 
strains are plotted outward from and normal to exterior outline of valve from points where 
strain gages were located. Contours were taken from X-ray photographs, except dotted por-
tions, which were taken from drawings. 
z 
» 
n 
» 
-l 
z 
z 
o 
0'1 
T1 
<D 
VJ 
P> 
Strain 
o Longitudinal 
o Circumferential 
(b) Valve B. 
NATIONAL ADVISORY 
COMMITTEE fOR AERONAUTICS 
Figure 3. - Continued. Cross-sectional view of test valves. Space scale, three times full 
size; strain scale, 1 inch represents 200 microinches per inch for IOOO-pound tensile 
load. Tensile strains are plotted outward from and normal to exterior outline of valve 
from points where strain gages were located. Contours were taken from X-ray photographs, 
except dotted portions, which were taken from drawings. 
T1 
<0 
VJ 
c:r 
z 
» 
(") 
» 
-I 
z 
z 
o 
01 
o Longitudinal strain 
(c) Valve C. 
NATIONAL ADVISORY 
COMMITTEE FOR AERONAUTICS 
Figure 3. - Concluded. Cross-sectional view of test valves. Space scale, three times 
full size; strain scale, I inch represents 200 microinches per inch for 1000-pound 
tensile load. Tensile strains are plotted outward from and normal to exterior outline 
of valve from points where strain gages were located. Contours were taken from X-ray 
photographs, except dotted portions, which were taken from drawings. 
z 
}> 
n 
}> 
-i 
Z 
z 
o 
0\ 
.,., 
<D 
VI 
() 
200~i------~------~------~-------r-------.------~------~------~-------r 
150 1 l~ 1\ I Y" J< -:::-Al If/~ 
• 
s= 
...-4 
......... C 100 
o ...-4 
0 
J" 
() 
...-4 
El 
.. 
c 
~ 
'" J.. 
+' 
CI) 
50 
0 
Valve 
o A 
o B 
6. C 
NATIONAL ADVISORY 
COMMITTEE FOR AERONAUTICS 
-50~1--------~--------L-------~--------~--------~------~--------------------------~ 
o 1 2 
Distance from point d of seating face along surface of valve, in. 
Figure 4. - Comparison of longitudinal strains for valves A, B, and C. Tensile load, 1000 
pounds. 
3 
-n 
to 
.f>. 
z 
» 
n 
» 
-i 
z 
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Strain-gage Study of Internally Cooled Exhaust Valves Having Various Throat Designs

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