-
AD-779 087
ELECTRON BEAM ANALYSIS OF mFHE PROPEl-TIES OF MOLECULAR NITROCEN
AND NITRICOXIDE IN THE AFFDL 2-FOOT ELECTROGAS-DYNAMICS
FACILITY
S. L. Petrie, et al
Ohio State University
S I• I.[ II
I Prepared for:Air Force Flight Dynamics Laboratory IFebruary
1974
H
National Tehnlincal Informiation Service jU. S. DEPARTMENT OF
COMMERCE5285 Port Royal Road, Springfield Va. 22151
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4. TITLE rMnd Subtitle) 5 TYPE OF REPORT Ai PP,•OD COVERED
ELECTRON BEAM ANALYSIS OF TILE PRCVERTIES OF Final
MOLECULAR NITROGEN AND NITRIC OXIDL IN TilE AFFDL 1 Dec 71 - 22
Aug 73
2-FOOT ELECTROGASDYNAMTCq FACILITY 6. PERFORMING ORn. REPORT
NUhoDEr
7. AUTtIORta) A CONTRACT OR GRANT NuMSERI(a`)
S. L. PetrieJ. J. Komar F33615-72-C-1023 R/
9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT,
PROJECT, TASK
AREA & WORK UNIT NUMBERS
The Ohio State University Research Foundation131.4 Kinnear
RoadColumbus., Ohio 43212 Project Number 1426
It. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE
Air Force Flight Dynamics Laboratory (AFSC) February 1974United
States Air Force I1. NUMER OF PAGES
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19. KEY WORDS (Cont~inue on reverse aide it nocoafcry said
Idontify by 1 ¢10C- Iulmboe)
Electron beam instrumentation; Arc-heated wind tunnel;
ElectrogasdynamicFaility; "V Molecular nitrogen; Nitric oxide;
Vibrational temperature measure-iiment; Number density measurement;
Inviscid flow analysis
20. ABSTRACT (Collnue cm ravtivs a•, do It noceaea'y and
Identify by block number)
The electron beam fluorescence technique was used to measure the
vibra-
Lional temperature and nuaber density of molecular nitrogen and
nitric oxide
at the exit of the 7-inch conical nozzle of the Air Force Flight
DynamicsLaboratory 2-Foot Electrogasdynalnlcs Facility. In
addition, the vibrational
temperature and species concentration of nitric oxide were
measured at theexit of the 19-inch conical nozzle. Tests were
conducted at reservoir pres-
sures of 250. 350, and 500 psia, with reservoir euthalpies
varyiLug from 2127to 5931 BTU!b. Theotc results assuming
flaite-rate chemlcalIJAN 73 1473 EDITION OF I NOV 65 IS OBSOLFTE
L_
UNCLATISSOF P0 SECURITY CLAS,%IFJCAliO"H OF THIS PAGE flfl)en
Doesa•leef
/N
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J
UNCLASSIFED
SUCUAITY CLASSIFICATION Or Tjl PAGC(eWhe.n [e, tn Entermd'
notiequilibrium were compared with the experimental data. For
the 7-inch nozzletests, poor agreement between the measured and
predicted nitrogen concentra-tions was obtained. The
excitation-emission mechanisms for elcctron beamexcitation -If the
NO# system in NO-air and NO-nitrogen mixtures were investi-gated
and it is shown that the excltation is dominated by secondary
electronsresulting from beari-induced ionization of molecular
nitrogen. Application ofthe electron beam technique to the
measurement of nitric oxid- r,-mb-r cntitiesshowed that the
nonequill'Uium theory over-predicts the amount of nitric
oxidepregent in the expansion process. Reasons for the
discrepancies between thetheoretical and experimental results were
examined.
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S•tCURtTY CLA•S1FICATION OF THO1$ PAOrfl:Wran bJare hoir ...
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vrU.S.Governmont Prinlno offlco; 1974 - 758-433/533
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AFFDL-TR-74-8
ELECTRON BEAM ANALYSIS OF THE PROPERTIES OF MOLECULAR NITROGEN
A
AND NITRIC OXIDE IN TILE AFFDL 2-FOOT ELECTROGASDYNAMICS
FACILITY
9I
S. L. Petrie
J. J. Komar
Approved for public release; distribution unlbif~ted,
JI (II
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FOREWORD
This technical report was prepared by S. L. Petrie atid J. J.
Komarof the Aer-nautical and Astronautical Research Laboratory of
The Ohio M
State University Research Foundation on Contract
F33615-72-C-1023(OF 3361-Ak). The rese•rch reportud here was
prformad on Task 142601.H. Lee of the Air Force Flight Dynamics
Laboratory, Wright-PattersonAir 'orce Base, Ohio war the project
engineer for the e¢ntract and forthe facility tests.
This report covers work conducted from 1 December 1971 to22
August 1973.
The manuscript was released by the authors in August, 1973,
forpublication as a technical report.
This technical report has been reviewed and is approved.
Chie , Flight Mechanics Division
Air Force Flight Dynamics Laboratory
lii
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ABSTRACT
: Tihe electron beam fluorescence technique wras usied to
mnouear theS~vibrational temperature and 'utudber densiLy of
molecular nitrogent and
nitric oxide at the exit of the 7-inch conical nozzle of the Air
ForceFlight Dynamics Laboratory 2-Foot Electrogasdy-namics
Facility. Inaddition, the vibrational temperature and specites
concentration of
S~nitric oxide were measured at tha exit of the 19-rinch conical
nozzle.Tests wer-e conducted at reservoir pressures of 250. 350,
and 500-.•ola,
S~with reservoir enthalpies varying from 2127 to 5931 Btu/ib.
Theoreti-S~cal results assuming finite-rate cem~eical
nonequi1ibrium were compared
with the experimental data. For the 7-rinch nozzle tests, poor
agree-ment between the measured and predicted nitrogen
concentrations wail ob-tained. The excitation-emission mechanisms
for electron beam excitationof the NU y syutew in NO-alir and
NO-hitrogsen mixtures were investigatedand it is shown that the
excitation is dominated by secondary electronsresulting from
beam-induced ionization of molecular nitrogen. Applica-tion of the
electron beam technique to the measurement of nitric oxidenumber
densities showed that th~e nonequilibrium theory over-predictsthe
amount of nitric oxide present in the expansion process. Reasonsfor
the discrepancies between the theoretical and experimental
resultswere examined.
il!i
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I
TAELE OF CONTIJT9 -
S ction
I INT130DUCTION 1
11 EL1CTRON BEAM MEORY 2
A. (OEIIEAL CONSIDERATIONS 2
13. VIrPRTIONAL T4MPERATITRE M=UR W-ri 3
C. NUMIER DENSITY MEASURM T 4
III CALIBRATION UFElIMENTS 10
A. GENERAL A-PPROACH 10
B. ELECTRON BEAM GENERWATOR 10
C. INST•UMENTATION 10
D. CALIBRATION RF-3ULTS iii
IV APPARATUS AND PROCE)URES 21
B13 ELECTRON BEAM SYSTEM 22
C. TES3T PROCE)URES 24
D. DATA REDUCTION TDMHNIQUES 24
V R0I9ULTS AND DISCUSSIONS 29
A. Tii)ORE!LICAL ANALYSES 29
D. NOMINAL RUN C0ONDITIONS 29
C. PROBE DATA 29•
). VIBRATION11L TEMFERATUREb 35
E. NUMBER DENSITIES ?i3
VT CONCLUSIONS 52
A. ELECTRON BEAM ¶E"11NIQUES 52
B. TIHEORIU ICAL-FIXPERIMENTAL COMPARISONS 52
REI' ,-t'ER cN C i;3
v1
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I3I
T alble
IPROBE LOCATIONS DI TNCORE DOWNSTRFAM Or, NOZZ LE Xr 21
1.1 QUENCHING, CONSTJWNS 27
MI N {AJ M A RESERVOIR CONDITIIN SUINVART 30
LIST OF ILLUSTRATIONS
3. 1atio of Intensitics for the (1,5) and (0,2) Dands ofthe NO ý
and (0,I) Mnd (1,2) Swids of h Nte Systems 5
2 8(TV)/S(300 Kt) f~or (O,v") anid (1,v") Bwikdb of the
N&,-and NO y Systee 9
3 Electron Beam Genertor-Gap Lena Schematic 111
It Elactrin Beam Gener•'(Aor Scheiau*.lio 1.2
5 Calibration Inatrume ,ttiou Schematic 13
6 n1tena:1ty of NO 7 (0,2) Rime in Va'iouo Gan Mictuarea 15
7 ImensLy of NO y (1,5) Pxnd In t•.ioug Ga6 Mixtures 168
Spectrca Sean of NO 7 Systmu in 670 NO, 3D% Air 18
9 ,1/I for NO y (0,2) and (1,5) Bands 20
10 Inst- rumet ta tion S clwwa•a Ic 23
11 Typical Riun Record of Spectral SCarT p=
12 Test Chamber Pistollation in the 2--Foot EGF 27
1.3 Pitut Presoure Sauveya at Run Condition 2; 19fInchNozled Po
0 350 pala 30
14 Pitot Preseýxre Surveys at Man Conditlo' 3; 19-InchNozzle; po
= 500 pola 1
V1
-
aa
LTST OF ITaISTRAlTIONS - (Contniucd)
15 Pitot 1ressure Surveyi at uin Condrition 1; 7-Inch
A
No-zln; p- 0 250 pisi 3
16 Pitot•'ressur-e Suiwveys Rt- Run Condition 2, 7-nm ahuNozle;
N =- 350 pain 33
17 Pitot Pressure Surveys at Run Condition 3; 7-InchNozzle; Po =
500 pala 34
18 Pitot Pres.ure Surveys at VWaous WAxa1 Stations -Run
Condition 1., 7-Inch Nozzle 36
19 Pitot Pressure Surveys at Various Axial Stations -ffim
condltIon 2- 7-1nch Nozzle 37
120 Pitot Pressure St•ukway at Various AxalJ Stations -Run
Condition 3, 7-Inch Nozzle 38
21 Axial Centerline Pitot Pressures; 7-Inch Nozzle 39
-L rncbr.rs 7-fnch Nozzle 1,
O2 NO Vtbratloail Temperatures; 7-inch Nozle1It4 NO Vibrational
Temperaitues; !9t]Thch Nozzle 42P-5 N, Nu•ber Densities at Rxin
Condition 1; 7-Tnch Nozzle 44
26 N2 NMmber Denitles at Ru, Condition 3; 7--Inch Nozzle 45
27 NO Number Densities at Run Cunittion 2; po ) 350 psia;7-Inch
Nozz?1.e 47
28 NO Number Densities at han CoudItion 3; • = 500 psia;7-inch
Nozzle 148
29 NOD Number Densities at Run ConL•ition 2; Po w 350
psia;19-.Inch Nozzle )49
30 NO Number Densities at Rua Condtiocnj 3; po - 500
pl.a;19-Inch Nozzle 50
vii
-
U
U
fj frt'.ction of photons a ~~b~o'h, by i#peclcn J i•
&rotud
G~o)vibr~tcnn1 te~rm value in j•roumnd elmctrxonic enurgy
utata
h) LagnatLon wnthalpv
! ph~om].t tJ •S'r ourr StFII
pho toio0ulrtplier current with no oaccltct'ton by
uocondnryI
p~rt~fŽffim .1ort.i Wel" ý,haissvUn
N to~a1 numbe r d1,l, It:y
Nk nusbper doi~aty of lpight ~ 1Sfraction oquefcphono deneliy of
sipi k
! ~NN2,[N2 ] N2 latiblr density
NNOC O NO numib1lCr densiity
p statrtc pressAure Ip' quenching prmvalue i
Pooatnit.plon (reservoir) ccrur
Q (vi) cro~s iptoct ltn ipior cxcatt. h noion by pc Ltatn b
elcL:oo
vARM
alactan bem crren
-
QkO (v,) crotai r.csion for "~Citrtonti Of idr~cien k by
u&ccondariFeiect roan.
Qv•T (VC) total cross aatinn for lnnixatl.n *t Oper-le-a k by pi
trza-r;
Shlat trailpfer rite
q(v' v ) Franck-Condon foartor for v' ! v" trgnstt)nn
S(TV) vibrationl tCamparature correction to dansity
T taiitftlational temporature
Tv vibrational tempera~t re
t time
V, v ,vo vibration~l quanLum numbers
v g'.primary electron velocity
vs Aoaoiddry 0"•Lr".. t Vret locitvy
Zkj collision fraquency for collitaor.n betwean specl.es k aind
j
%,. vj %vatwivuumbar for j r arsivion
meAn frov pWth r*-lnctloii for secondary etectronn
Mans dtengity
c for pro-run calibration conditions
o for reservoir conditione
SC for condltlonin ii i t t. - tit chaimb)r
I for Chnnnel I
I1 for Channel II
*' for prIfrte-., tXC Ic ed elect ronic OtiO-gy SLatc
Ix
Lo
-
I. 1N1TRODUCTION
Arc-heated wind tunnels are generally characterized by a
highdegree of thermodynaric and chemical nonequilibrium wit'hln the
expansionprocess. To predict test-section gas pro !rtiags end
properly interpretmodel data obtained with such facilities, an
accurate theoretical analy-
sis of the flow process employing finite-rate chemical and
thermodynamicreactions is required.. The accuracy of the analysis
depends directly onthe applicability of the kinetic model (i.e.,
the set of reactionsemployed) and the availability of the
appropriate rate constants.
While certain wind tunnel calibratiou data (i.e., pitot
pressure,flow velocity, stagnation point heat transfer rate) are
relativelyineependent of the detail.ed ther.mochemical processes,
other calibrat. onf, ctors such as the static temperature, Yach
number, Reynolds number,etc., are not. Since many of the quantities
which cannot be directlymeasured must be Imown to relate the wind
tunnel data to equivalentflight conditions, an accirate theoretical
model must be available.The accuracy of such a model can be
determined iV appropriate measure-ments can be made which will
allow comparison of the theoretical resultswith experimental
data.
The chemical species of interest for much of the operating
rangesof typical arc-heated wind tunnels consist of: N2 , N, O, 0,
NO, NO+,and e-- White N__ 0. and o0 mrkeP up at. least 95% of the
gas mixlture.nitric oxide can be extremely important in drtermining
the gas composi-tion. The nitric oxide shuffle reactions, N2 + 0--
NO + N,N + 02 -• NO + 0, and N2 2 02 - NO + NO, are binolecular and
hence, areextremely rapid. In certain operating ranges, these
shuffle reactionscontrol the rate of oxygen recombination in the
nozzle expansion pro-cess, and thereby heavily influence the
resulting gas properties at thenozzle exit. Hence, measurement of
the properties of nitric oxide canbe extremely useful in
determining the accuracy of the shuffle reactionrates and their
:elative effects on the resiulLs o0 the theoretical
pre-dictions.
A series of expertrients hi s been performed in the AFFDL
2-FootElectrogasdynwa iFccility (EGF) in which the electron beam
diagnostictechnique has been applied for the measurement of certain
gas properties.In Ref. 1, the technique was applied for the
measurement of the vibra-tional temperature, rotational
temperature, and number density ofmolecular nitrogen. In Ref. 2,
the species concentrations of molecularand atomic oxygen, and the
vibrational temperature of molecular oxygenwere determined.
Application of the electron beam Uiagnostic techniqueto tht
determination of the properties of nitric oxide were investigntedby
Petrie and Komar. 3 The calibration experiments.of Ref. 3 have
beenextended and the diagnostic techniques have been applied for
measuringthe properties of nitric ox'de in the 2-foot EGF operating
at ncminalflow Mach nunbers of 8 and 1.0. In addition, the
vibrational temiperatureand number density of molecular nitrogen
have been measured at a flowMach number of 8 to extend -the lowter
density measurements of Ref. 1.
I-
-
As in Refs. 1 and 2, the electron beam data are compared
with
usual facility operating parameters and nozzle exit pitot
pressures toletermine the properties of the test gas at the
measuring station. Theseexperimentai results are compared with
those from the theoretical analy-sis to provide additional
information useful for assessing the applica-bility of the
theoretical model.
The general theory for electron-induced radiation in nitric
Oxideis summarized in Section II. Section III describes the
experimentaltechniques used, and the results of certain calibration
experiments.
The remaining sections describe the application of the
diagnostic tech-niques in the 2-foot EGF.
II. ELECTRON BEAM THEORY
A. G2MERAL CONSIDERATIONS
Radiation intensities sufficient for accurate determination of
gaspropeaties in an arc-heated wind tunnel can be obtained with
electronbeam currents near 20 mA at beam voltages fram 5 to 75 kV.
The beam isprojected across the flow, and the interaction of
electrons with gasparticles produces a column of radiation which is
nearly coincident withthe beam of electrons. Profiles of gas
properties are obtained byex•inLing va:rious points along the
length of the beam. High-beam volt-ages are required to obtain good
spatial resolution in the measurements;at low-beam voltages and
high gas densities elastic scattering of thebeam electrons is
severe.
When an electron beam is passed through the flow at the
nozzleexit, radiation is observed due to bombardment oa most
species knowva toexist in the flow field. The radiation resulting
froa excitation ofmolecular nitrogen and nitric oxide is of
particular interest.
The predoainant radiation due to excitation of molecular
nitrogenis the first negative system of the ionized nitrogen
molecule (N21')."The most intense band is the (0,0) band at 3914 A.
Much experimentalwork (summarized in Ref. 4) has been done with the
first negative systemin nitrogen and air to verify the
applicability of the diagnostic tech-nigue. Deteails of the meho.ds
can be found in R~efs. i' and 1-79
Electron beam excitation of nitric oxide results in observation
ofradiation in the y, Ogawm, asd Feast syste•n,.3 In air flows, the
vsystem 'is useful for vibrational temperature and number density
measure-ments at wavelengths below approximately 3044 L. At higher
wavelengths,the y bands are o~rerlapped by bands from the N2+
systems. The Feast andOgawa systems appeaa1 only weakly at
wavelengths between 5800 and 6100and relatively little is known of
their strueture. The uncertaintiesassociated with these systems and
their low radiation intensities makesthem unsuitable now for
electron beam diagnostics.
-
ITe electronic transition comprising the NO y system is denoted
byNO(A 2 Z+) -> NO(X 211). Emission is excited by collisions
between electronsana nitric oxide molecules in the ground
electronic energy state NOU(X2 ).oADetailed considerations of the
excitation-emission process in pure nitricoxide are given by Petrie
and Komar-: and will not be repeated here. Itshould be noted,
however, that the transitions are resoneant. That is, Uthe
excitation and emission processes connect the same electronic
statesso that self-absorption of the radiation is possible. The
analysis ofRef. 3 indicates that self-absorption can be neglected
for nitric oxidenumber density-path length products at least up to
10s m 29 for tran-sitions which do not involve the ground
vibrational energy level. Inthe studies reported here, only those
bands not involving the greou•n)advibrational energy state were
used so that self-absorption effects canbe neglected.
For both molecular nitrogen and nitric oxide, it is assu3med
thatexcitation occurs with no perturbation in the rotational and
vibrationalpopulation distributions in the ground electronic energy
s.-ta-te. Sincethe Born approximation is assumed to apply, onLy
those tran-sitions whichare allowed by optical selection rules are
considered. Hence. both theexcitaLAon and emission transitions are
assumed to be governed by theFranck-Condon princip -.
The rotational stractu-, of the NO y bands is quite
complicatedsince the emission is a 2 it'--I transition. Separation
of the individualrotaioa lnes requi.res both hlitg- spectr... l.
r-so lVery intensae"radiation so that an acceptable tign,•,o-oise
rato e.n be obt(ain.ed6As discussed in Ref. 2, for rotational
tewmeraýture ,ca."u.eaIen there islittle need to resolve the
rotational & Uixre of bnds other thenthose in the Nf+ first
negative systa ho rafpid equilibration of therotational. energy
modes -f all& heavy tes with the. tnrns ation',&ener&y
mode allows the rotati.ona2 t", atvxe of each species toassumed
equal to the translational ;1ým. ature of the gaws, •exnce,
themeasurement of the rotational i peratou: of- molecula:r nitrogen
will.suffice to describe the rotation, aislational temperatures
ofall heavy species.
D. VIBIATIONAL TEMPERATUMhL FXSURE.M-TWT
The ratios of intensities of two vibra)tional be,)nds in both
tle Nflfirst negative and NO 7 systems ,\rno determined by assuming
that thepopLlations of the vibr'ational energy levels of both N2
and NO can bedescribed by Boltzmenn distributions witn vibrational
tekperatureswhich need not be equal to -the translational
temperature nor equal toeach other. The ratio of intensities of two
vibrational bands is givenby
7%q2(vj.',vo) eGvhev 7 v2j3q(vp',v 211 )(V2) eV "
VO V"
3 JIM
-
where 0 a and q2 are the Fr anck-Condon factors for the emission
transi-dions, q(v 't,vo) is the Frauck-Condon factor for the
excitation transi- Ution from the vo vibrational energy level in
the ground electronic statejto the v.1 -vibrational level in the
excited electronic energy state,and G(vo) is the vibrational term
value in the ground electronic energystate.
From Eq (.), the ratio of intensities of two bands in the
emissionis a function only of the vilbrational temperature of the
molecules inthe ground electronic energy state. The ratios of
intensities of variousband combinations for both molecular nitrogen
and nitric oxide are shownas fu•nctions of vibrational temperature
in Figure 1. The Franok-Condonfactors employed to construct Figure
I are given in Refs. I and 3.
With the assumption of direct excitation, the vibrational
tempera-tures are determined by measuring the relative intensities
of the vibra-tional bands and consulting the curves of Figure 1. It
is notable thatmuch greater sensitivity to vibrational temperature
is obtained withmolecular nitrogen than it is with nitric oxide.
The relativelv smallvariation in intensity ratio with vibrational
temper•ature for nitricoxide places severe requirements on the
elactro-optical system employedto make the band intensity
measurements.
C. NUMBER DENSITY MEASIRDET
It is a comnion practice to determine the number density by
measuringthe intensity of one or more vibrational bands which
appear in the beam-excited emission. In order to interpret the band
intensity in terms ofnumber density, the excitation-emission
mechanisms which lead to theradiation must be known. It is well
known that for molecular nitrogen,the N_2 + first negative system
is excited primarily by beam electronsand that secondary electrons
have a negligible effect. However, becauseof the low excitation
energy of the NO 7 upper state (5.2 eV comparedto 18 eV for the
N2+(B 2 Z) state), secondary excitation mechanisms maybe important
in p.roducing the NO y system.
As described in Ref. 8, the rate of excitation of gas molecules
toexcited electronic energy states due to excitation by primary
andsecondary electrons can be given by
NeveNQjis(vs) r, NkQkT(re)
NeveNjQo(ve) + k N it + (2)
k
where the first term accounts for excitation by primary
electrons andthe second term allows for excitation by secondary
electrons. Ndenotes the number density of excited species, No is
the electron
-
4000- f
ujjS.j3000- -]!
2000--zI
NO `5_)00:2
> 1000
00 2 3INTENSITY RATIO
Figure 1. Rltio of Tntensities for the (1,-5) and (0,2) Bands
ofthe NO 7 and (0ý,I) and (1,,2) Bands of the N2 + Systems
5
-
number density within the beam, ve is the velocity of the
primaryelectrons, Nj is the number density of the species in the
groundelectronic energy state, and \s is related to the diffusion
coefficientof the secondary electrons. The quantities Qo(ve) and
Qj1 (v&) are thecross sections for excitation of species j by
primarr electrons andsecondary electrons and, QkT(ve) and Qks(vs)
ar\. the total cross sectionsfor ionization of species k and
excitetion of species k by secondaryelectrons.
Sin6e the NO y system is resonant, population of the upper
electronicenergy state as a result of absorption of resonant
photons should beincluded in the analysis. In addition, excitation
cauved by the colli-sion of ground state molecules with
electroniccally excited particlescan be included. The rate of
excitation due to these two nxehtanismsis given by
d-" A + f ZjtjNk* (3)k
where f1 is the fraction of the resonant photons absorbed, Aji
is thetransition probability for spontaneous emission, and ZkI is
the frequencyof collisions between grou..nd state molecules and
excited p crticles ofspecies k. Note that induced emission is
ignored in Eq (3).
The collision frequency Zkjt is given in the same form as that
forusual binary encounters except that the cross section for
excitationis employed instead of the simple kinetic cross section.
Hence,
[k 4Nj Qkj &V/-fri (4)To allow explic.it appearance of the
number densities, the collisionfrequency is rewritten as
Zkj - ZkJ/Nj (5)
De•o-pilatIon of the excited state is assumed to occur due
to
spontaneous radiative transitions and collision quenching.
Hence,
Nj*kAii + E Aj+ + Z NkQJc (6)
6
-
where Qkc is a "tquenlching speed" with iunts of cross section
times speed.8
In the steady stbate, Eq, (2)-(6) give the concentration of
excitedparticles as
xI.x. i + 101tl/iN j - F.. . . . ... ..
Ajji + A k
NeVeNjQs(vs) 1 NytQT(Ve)it + • ZicjNicNj (7) -
NeveNQ(ve) Qs(V) + XS2 kt INItkSvsItk
where Nkc (Aji + A)/Qitc is considered a quenching nwumber
density8
and A = 2 Ajk,It 7 j
The intensity of the radiation is given by
I= Njx'hcvjiAji (8)
where h is Planck's constant, c is the speed of light and vjL is
thewavenumber of the j -> i transition, The output of a
photomtultiplierviewing the radiation is related to the intensity
by various sensitivityfactors which arise because of absorption by
optical components, theinstrument function of the device used for
spectral resolution, thephotomultiplier gain, etc. These factors
are combined into a singlecalibration constant, ci, which also
includes the multiplicative con-stant which relates Ne, 7e, and the
electron beam cross-sectional area-to the beam current, J. Hence,
the ratio of photomultiplier signal-to-beam current is given by
Aji + A Nk/Ni
)NkQks(vs) + is t k
7
-
The constant Cj must be determined by calibrating the
entireelectro-optical system. This is usually done under
room-temperatureconditions. lot-ever, the intensity of at
vibrational band depends uponthe various factory of Eq (9) and the
vibrational temperature. Toaccount for the vibrational temperature
effects, the photomultipliercurrent can be given byl'o
[a i (c1S(Tc$~;AJ 1 - _ + r+d A •k/Nk -j
Qs ( "s) NkQkT(ve)
Qo(ve) + k ( 0 )k1NkQk"(v)+ Nk+ I O
WhlereJ
q v) q(v°'v') -G(v0 )hc/kT1S(Tv) Q-(Ti )q(v ' ,v") ao
S(TV - -I v•'V •v "11 "• v CV V )F)and S(Tc) i.o S(Tv - 300 K).
The functions S(Tv)/S(T0 ) for the v' 0and I progressions for the
N2+ first negative and NO y systems aregiven in Figure 2.
In a strict sense, the correction for vibrational
temperatureeffects applies only to that portion of the excitation
due to primaryelectrons (a similar form can be written for the
resonant absorptionterm). Collisional excitation by secondary
electrons and excited parti-cles may be accompanied by perturbation
in the vibrational populationdistribution so that Eq (11) no longer
applies to the entire excitationprocess. In addition, preferential
collision quenching of variousexcited vibrat-ional energy levels
may occur. These effects must beevaluated in specific applications
before the excitation-emissionanalysis can be applied with
confidence.
47
8 4
-
I
0 -o 1
I__ . . I '4.I•e e . .. . IId d
( I~)$(± mu0±9 !9 JINI
z I.9
-
II
III. CALIBIXWION EXPERIMNiTr IA. GENERAL APPROACH
A series of calibration experiments was conducted to evaluate
therelative importmnce or the various excitation mechanisms
accc4ýpaflyingelectron excitation of nitric axide. The variations
of the radiativeintensities of the (0,2) eand (1,5) bands of the O
y system were IiW.nveaItigated over a range or gas density in pure
nitlic o~ctde, nitric oxide-air, end nitric oxide-nitrogen
mixtures. The experiments extend thoseof Ref. 3 which were
conducted only in pure nitric oxide. The resfltsare inteapreted in
terms of the excitation-emission analysis of Ref. 3and Section
11,
B, UEECTRON DFAM GENERATOR
The electron beam generator used for the calibration
experimentbsis shown schematically in Figure 3. The system differs
from thatdescribed in Refs. 2 and 3 end nsed in the previous EGF
experimentsI.The present electron beam generator allows
accelerating potentials up -•to 75 kV, while the older version was
limited to voltages up to about20 kV.
The electron beam generator cone'ist's of a duopl.asmeýtron
electronsoCuree, a gap Lenas IoM b rc g and la eadn b teer"L,•gand
focusing systems. The lens elements are mounted Inside a
6-inchstandao-d steel Ueo which is connected to a 6-inch oil
diffusion pvumpA baffle is used betwee the dlffusion pump aund the
be•a chamber toreduce bacastreamuing of0 diffusion pump oil. The
electrons exit frcuthe bean chlmtber through a O,03-inohldiameter,
0.30-inch-long exit Achannel. A"
The maximum acceleration potential is 75,000 V with a maximum
boomcurrent or 60 mA. To minimize defocusing of the beam as it
traversesthe drift tube and passes through the exit orlflce, the
electrons areaccelerated from high potentials toward ground
potential. An electricalschematic of the beam generator system is
given Jn Figure h.
The main oplatiei instinmentb-ation system employed in the
ealibrtationstudies is shown schematically in Fig1ure 5 and is
deseribed "in detail inRef, 3. Spectral resolution was
accomplished( with a Jarrell-Ash 0.5-MrEbert s•cmaing spectrometer.
The grating was rtled with 30,000 lines/il.yielding a dispersion of
i6 A/mm and a maxn:Dilm resolution of' 0.2 A. AnEMil 62568
photonnultiplier was used with -the spectrometer. The
photo-currents were measuried and amplified with a Keithley Model
10-.7 ptcoeamueter.The beam current won mo.It-ored by measutrif ng
the voltage d(rop ao•rO•s t.he
30
-
F771
III
vvIf•I III a1 I4 ... . I•
-
4'r
r 7
tYI:=c IT---- IL•44 !-L .,
11! L] " : .• •,•' 1W _ >
12
I .- 6 I-•o--•At••L' ... "']tilt•°..\Q -a. " ....
• " _I') _
,1.2
_I-
-
'F
0 °O"n t°
[Iii
.OD
9-
tAwl
11-: ES reni I
li UI TV
13
-
beam current nmnettr. The outputs from Lhe picoanne-tor and beam
currentawnineter entered on on-line angiog rcamuter whero the
ratios of the photo-mnuitplier and beam current signals were
ronnad, and the results weredisplayed on X-Y p•uLLerv. Since the
photcz!ailxli"ar outputL vD.rltsI I Aaery 1; with hoeCurent,, tlie
r atloc of a ±giwd o JIn n tUne reasaaurea ol'the relative
intensity of the region of the spectrIn uindetr investigationwith
the epectraneter1
For the calibration e2pairmenta, the lleotron beam wee
projectedinto mi l8-inch-dimtetr, l8-inch-iong cadimiumr-plated
steel test chamber.The eloctron beaw Senerator wva.. electrical.ly
laotated fiN= the testchamber so that the antire chamber nerved an
a Varadey cage for themiatsu,,ment of boom current. The electron
beami wan captured in a water-cooled 9qG elbow to eliminato
baok-eoattering of tow energy electrons.Previou teats have
damanstrated that this configur'ation virtuallyelilinatea radiation
due to excitation by aecondary eleaetrons resultingfrom baaburdmont
of the chamber waJ.is by bemr. electrons.
Mixtures of nitric oxide-nitrogan emd nitric oxide-air were
suppliedthrcigh two separate flow metering systeas. Nitric oxide
was suppliedby one metering ayetnm, while either air or nitrogien
was supplied bythe other.l The grases were uixerd yn-n-ndt-iertl-y
in the teat chaember.Dynamic mixing was chosen over the simpler
procedtre of using pre-mixedgasoe to roduoe the n•hmical reactions
which occur beLween niýric oxideand molacular oxygen i No-alr
mixtures.
'Clie teote were conducted by voc•ctwbig thu Ldt. eliooer •vo a
Prom-sure less th, - I =1 Hg and pumping on the system for at least
30 minutes.The doa1red flow rates of nitric oxide mid tie aecond
gao were theneatablilhed it-lh the flow maters. At that time the
valve between thevacuum pump and the toet chamber was cloved and
the output of the photo-mulItiplier d.vl.dod by bamun current was
plotted versus the chambor pros-su•re on eu X-Y plotter, izaw
phcd;oi•m.ftiplAer ad beam current signalswere also plotted versul.
proeu~ro. The rate of pressure rise was lowenough to asure that all
electrical components responded to the changein signals
acccmpanying the pressure increases.
The presoure in the teot chamber wun measured with a
varlablereluctance presaure transducer.. The electrical output of
the trmasducerNqao sent to the tuilog computer wh-er veaious
ua.Lbr-•tLon consttnta wereapplied 'o obtain correocted pressure.
The result:i4i pressure was are-cor'ded on X-Y mtotters.
D. CALIBRATION RESZULTS
The inteisllties of the NO y (0,2) tnd r,) hands are
pklotitedversus NO partial pressure in Figvrea 6 and 7. It is clear
that theband biten ities do not correlrte with the NO pirtial
pressire, W1.h0chwuniLd indicate the presnoce of excitaltion
nctchwaiiams in &adition, todni'ect excitation b bgane
clectro1s.
14
-
1 soI is i - i7S _____0 1
'I0
020
(0 •.r 0 i2 0
rC)3
- II II II II II
-D 0 0 0 0 0.% I1CL Z Z Z Z Z 4ws .Mi
Sb Iv P
--
-- " 0
! . 0
o. q • o q o
SiLINnl AdW dlIBdV -iN2-1flt9 PV'A9/ I.LISN•J.NI
-
0o1 I I T Fo ,.'
oZ 0: 1') 0
-" 1-0 I--C 0 0. 0W -00000
0 0 0
z or: o
n 0 0 0 0
00K>0
LiU
Q.
-> 0 6)01 0
00
K>0 N
S0 0 F4
L __ .!L 1L J. J___
31V3S QJIVlI9.•V-lN8jnolL'8/AAISN-31NI
.16
-
To determine if the variations of band intensities versus
pressurein NO-air and NO-N 2 mixtures resilt from. overlap of some
other electronictransition, every known transition listed by Peerse
F.nd Gaydon9 in N2 ý,N2+, O_, and Oa+ was investigated. The
following bands of nitrogencould, overlap the NO r, (0,2) band: the
(14,25) band of the Lyman-Birge-Hopfield system, at 2481.7 Aý, and
the (O0-' 1 band of -the Herman-Kaplansystem at 2471.4 L. The NO y
(1ý5) band , y be overlapped by the (1,7)band of the nitrogen Fifth
Positive system at 2681.2 A, and the (0,4)band of Gaydon's T system
at 2678.7 A.
A spectral scan of the (0,2) band obtained vith electron
beamexcitation of a gas mixture with an NO-air number density ratio
ofapproximately 2 is shoin in Figure 8. The band profile is the
sameas that observed in pure NO (Ref. 3).
No evidence of b&L.d overlap can be detected in ayv of the
NO 7band profiles. In addition, the systems 1.sted above have never
beenre'oorted in excitation of N2 by an electron beam. It is
concluded thatband overlap is not a likely cause for the oiserved
intensities of theNO Y bands in NO-air and NO-N 0 mixtures.
It is particularly noteworthy that the intensity variations
withpressure in NO-air and NO-N 2 mixtures are nearly identical
when thedata are examined at equal N2 partial pressures. It is thus
concluded -
intensities.
The intensity variations can be explained in terms of the
excitation-emission analysis of Section II. The intensity divided
by beem currentfor room-temperature mixtures is given by Eq (9),
repeated below forconvenience.
I~ci
1- '-
A-jL +A I
jQo(Ye)Nj +k _-----+Nrj
As previously discussed, the influences of absorption can
beneglected for the vibrational bands of interest here; hence, fj
is setequal to zero.
If collisions between ground state NO molecules and excited
speci escontribute significantly to the obqerved radiation, then
the intensitiesshould very quadratically with the gas pressure,
especially at low
17
-
4-ý1bUJ)
0>
0
NN
I:-•
° ,*i-.I
-
pressures where collision quenching can be ignored. Such a
quadraticvariation is not observed (Figures 6 and "7); henes,
excitation byexcited molecular and atomic species is ignored.
It is known that N2 has a large total cross section for
ionization4
so that it can be assumed that N2 dominates the production of
secondaryelectrons. In addition, because of the low excitation
energy of theNO(A 2 Z) state, it is assumed that secondary
electrons are lost primarilybecause of their collisions with ground
state NO molecules. It is con-sistent with the latter assumption to
assume that the range of secondaryelectrons is short in mixtures
contabning NO so that the secondaryelectron diffusion term in the
denominator of the second term in Eq (9)can be neglected. Hence, Eq
(9) becomes
It
or
I QN T1 e) NN (s
where. ••o VA Iit IntensitY which would be observed if there
were nocontribution due to excitation by secondary electrons. Note
that thisanalysis ignores all effects of collisions of particles
with the con-tainer walls.
To test the validity of Eq (13), the data of Figures 6 and 7
arepresented in Figure 9 as I/Iý versus NNq_2/NNO for several total
pressures.
Good agreement with Eq (13) is noted; the slope of the variation
ofI/Io yields a ratio of cross sections, QNk,T/QO, of 3.28. The two
datapoints obtained with air at a NN,/NNp ratio of 1.67 do not
correlatewith the other data. This may be due to the presence of
quenchingmechanisms involving molecular oxygen which would not be
present in aflowing system. For example, the reaction NO + 0.4 N02
+ hv may occurwith sufficient frequency to reduce the number of NO
molecules availablefor excitation by the primary electrons.
The calibration results are significant since they indicate
thatsecondary electrons provide the predominant excitation of NO in
mixturescontaining N2 . This is not observed in pure NO because the
yield ofsecondary electrons is much greater in collisions between
beam electronsand N2 molecules than it is in collisions between
electrons and NOmolecules. However, since the intensities of both
the (0,2) and (1,5)bands vary in the same manner with NN2 /NNo
(Figure 9), there is nonoticeable influence of the secondary
excitation on the band intensityratio. Hence, valid vibrational
temperature data should be obtained byreducing the band intensity
data with Eq (1).
19
-
•o°z z=
-C\j
Ii'
zz
0 00 i -i .LL -- J-jj 0- 0
•I/L.Lo 0
c'j
\--j--0
02
-
IIV. APPARATUS AND PROCEDURES
A, WIND TUNNEL SYSTEM AND INSTRUMENTATION
The experimental studies were conducted in the 2-foot
Electrogas-dynamics Facility of the Air Force Flight Dynamics
Laboratory. Thefacility consists of a direct current arc heater, a
conical eonver~ent-divergent nozzle exhausting to a free-jet cabin,
and a pressure recoverysystem. For the experiments discussed here,
nozzles with exit diametersof 7.0 and 19.4 inches were used.
Further details of the facility maybe found in Ref. 10. The typical
tunnel run time in these studies wasfive minutes,
A pitot pressure-mass flow probe and a stagnation point
calorimeter
were eamployed in these tests. The pitot pressure-mass flow
probe wasmounted on a survey strut which allowed the probe to
traverse the flowin a plane through the nozzle centerline. Pitot
pressures were measuredin 2-inch increments at three points below
the centerline, on the center-line, and at four points above the
centerline. Mass flow per unit area(00) was measured only on the
centerline.
IThe stagnation point calorimeter was a water-cooled
Gardon-type
cvlindrical probe with a hem~sph~rrn nose Another
arAdo-_•yp.calorimeter permanently installed on the tunnel
centerline was used toobtain a continuous record of stagnation
heating rate during the electronbeam experiments.
The location of the various probes used with the 19-inch
and7-inch nozzles are summarized in Table I.
TABLE I. PROBE LOCATIONS IN INCITES DOWNSTREiAM OF NOZZLE
EXIT
ProbeNozzle Electron Pitot
Dia. (in.) Beam Pressure19 4,06 6.06 1.75 23.81
7 3.06 1.56 0.69 6.06
A portion of the tests included radial pitot pressure surveys at
variousaxial stations in the 7-inch nozzle.
In addition to the flow field instrumentation , facility
operatingparameters were recorded during each run. These parameters
includedarc voltages, arc current, mass flow rate, water flow
rates, andtemperature rises.
21
-
V
The facility data were recordeb through the on-line
analog-digitaldata processor. Analog data signals from t'le tunnel
instlruentationwere entered through signal conditioning
equi-pulent, fed into the pro-cessor and computed, alid the results
stored ift digital foTh on magnetictape. Run identification and
time reference data also were recordedwith each data scan. At a
specific test point, the data chamels wererecorded at a rate of 16
samples per second f'•r a time interval of about10 seconds,
I•mediately after the conclusion of a run, the Individualscans for
each dUta point were time averaged to give the final data ata test
point.
B. ELECTRON BEAM SYST•M
The electron beam system employed in the 2'-oot EGF is"
identicalto that described. in Section II (Figure 3). The entire
assembly ismouited inside the wind tunnel test cabin so that the
electron beam wasprojected downward throough the nozzle centerline
at distances downstreamof the nozzle exits as given in Table I. The
electron beam power sup-plies and vacuum control console are
located in a control panel adjacentto the turnnel. The beam
generator is electrically isolated from thetest cabin so that no
special beam collecting device is required; thatis, the tunnel test
cabin serves &s the beam receiver.
!Lectron beau wiith C-urrento of approxijateay 20 mA ab
voltagesnear 40 IV were used for the tests. The beam currents were
determined.by measuring the voltage drop across a 570-$2 resistor
in series with -the beam current wmmeter. The beam currents were
monitored continuouslyduring the wind tunnel run by displaying the
voltage drop across theresistor on a X-Y plotter, 4,
The optical system for collection of the vibrational,
terperatureand number density data is shown schematically in Figure
10 and isdescribed in detail in Ref. 2. Spectral resolution was
accomplishedwith two 0.25-m Jarrell-Ash scanning spectrometers. The
spectrowetergratings were ruled with 1180 lines/mn yielding a
linear dispersion of33 A/mm and a maximum resolution near 1 A.
The spectrometers and imaging optics were mounted on a
traversingtable which was attached to the tunnel test cabin. The
table was movedin the vertical plane by a variable speed motor with
a total traversingcapability of 12 inches. A precision
potentiometer was attached to thetraversing table to provide an
electrical signal proportional to thelocation of the field of view
in the electron beam. -
Both channel I and channel II intensities were measured with
WM{. t6256S photomultipliers. Various load resistors were employed
in thetnode circuitry of the photomultipliers and the resulting
voltages were
measured with PAR Model 324 lock-in amplifiers. The chopping
frequencywas 167 11z. The signals fran the lock-in amplifiers were
dispJlayeddirectly on two X-Y plotters.
22.j
-
w a
i-. 1 4 I. 4 *.
L..L• F.l •LWCL
,... . _, 4, .4,
0
i.61
23 IiK
-
C. TEST PROCEDUMES
Prior to a wind tunnel toot, the spectral locations of the
spectrom-eters Wtre sot, ta 1011ow±-cOthdQdŽ disOchArge lamp which
yield5 radiationin thO NO y bands wOo turned on, alnd the chopping
wheel w46 starv•edThe lock-in amplifiers were phase locked to the
incoming signal and thelight intensity wAs adjusted to provide
photomultiplier outputs approxi-mately %qual to those cxpeoted
durinog the run, Thn phVtcvultlpilarWere allowed to fatigue under
this condition for at leaut 30 minuLesprior to the start of the
wind tunnel run. This prdoedure was nueessaryto stabilize the gains
of the photomultipliers and lock-in avaplifierr,thus eliminating
drifts ill the relative sensitivities of the tuochannels during the
course of the run.
Immedlately before the start of a run, the tunnel v•auum
systemwas started and a pressure of approximately 0.2 Torr was
maintained inthe tesot cabin region by leaking room air into the
vacuum pumps. Theelectron beam was turned on and was scanned over
the entire travel ofthe optical system. The signals from both
channels were recorded onX-Y plotters to provide the calibration of
the relative sensitivitiesof the two channels. During this scan,
the test cabin pressure andelectron beam current also were
recorded. The beam was extinguishedand the tunnel was started. The
time lapse between the calibrationexposure and the start of the run
typically was less than one mioute.
pitot pressure survey was taken and the centerline heat transfer
ratewas measured. At the conclusion .of the probing, the electron
beam wasscanned in one direction. The spectrometers were then
reset: to measurethe zero-reference signals and the beam was
scanned in the oppositedirection.
Run records typical of those obtainod with the NO y bands
areshown in Figure 11.
D. DATA REDUCTION TECHNIQUES
To convert data such as that of Figure 11 to temperature
anddensity, the sensitivities of both channels at each point along
thebeam must be obtained. Points at one inch intervals along the
beam inthe test flows were arbitrarily seiectad for data
reduction.
To calibrtt:eý the seustt.vlt;;tes of the two data channels for
nitricoxide measurements, a small test chamber was attached to the
end of thledrift tube of the electron beam generator. The chamber
was evacuatodwith a mechanical vacuum pump and nitric oxide was
continuously suppliedto the chamber through e precision needle
valve. The pressure in thechamber was measured with a variable
reluctance pressure transducer.The electron beam was projected
through the test chamber and capturodin a water-cooled 90 ' elbow,
The entire chamber was isolated
24
-
OD1-0-,
iid
•) C)
- IL : LL
V K(CT-VOS \kJVE•.IMiV),.LtSN3,.NI
25
-
olecteically from tlhe drift Lube so that it servoll as the beam
currentmeaouring device. The electro-optical system used for the
calibrationopeorl'Ponts duplicated that uafwd in the wind tunnel
runs. A photog.raphof the teot chamber installation in the EGF Is
shown in riguru 12.
'She Intenoitles of the NO y (0,2) and (l,$) banda at 2478 A
and2680 A waro measured with channels I and 11, reopoctively. The
calibra-tion constants, el, of Eq (12) wore determined from the
measured inten-aites 9 beau currenot, and pressure as
k(1/+3) 2 (1NO (1K/4)NNO 1i?~ NN2 NN 34
The ratio of nitrogen and nitric oxido number densities
wasdetermined by closing the valve whiclh connected the vacuum pump
to thetest chamber and measuring the rate of increase of the
chamber prasstur eboth with NO flowing at the rate used during the
calibrations and withno NO flow. The latter data were used to
establish the rate of airleakage into the chatmbor.
To allow the calibration results to be properly applied to
thewind tunnel experimenta and to provide a continual check of the
aensi-tivitios of the two channels, the ýnvensicy of the (1,3) band
of theN2+ first negative system at 4652 A was measured with both
charnnelsduring all pro-runm aid, otatic tes ch1a mber
call"brnvionn. This hanid wasC1hosen since its intensity under
static conditions was nearly equal totho•. obtained from the (0,2)
and (1,1) bands of nitric oxide.
The NO number desilties were obtained from the Intensitios of
the(0,2) and (1,5) bands with Eq (12) written in the following
form-
1 +YýNk /Nt4 N2k((15)
tS( /,S -c i+(i+ 3.28 N27N' ) -N2 (J(I/PJ)C
where (I/fJ)N and (l/pJ)N2 denote the invter.tties of the (1,3)
band ofthe N2+ first negative system obtained during the static
chamber andpre-run calibrations, r(Sct ...... .. The qe,,hig
,-i-denitv hor NAý I _f-N0O,was obtained from Ref. 11 and those for
N2 and 02 were 0rom Ref. 4,The quenching densities are summarized
In Table II. The quenchingfactor was calculated employing spacies
number densities resulting fromthe nonequillbrium calculations.
Since the quenching factor was nearlyunity for both the 19-inch and
7-inch nozzle tests, no iteration on thespecies concentrations was
necessary. The vibrational temperaturefactor, S(Tv)/S(Tc) was
determined from Che measur'ed vibrational tewper-atures and Figure
2.
26
-
Figure 12, Tent Chnamber Inst,,LJ.ttionLil tho 2-Foot BaF
TABLE, 11. QU4CIM.(NG CONS'•NTS
Specie• [i'.'Sp)NOLOp' rr W' (cn-' ) p' (Torr) N' (c;') p'
(torr) N' (oWn '")
NO 2.35 7.56 x. 1-01 3-1.30 3.61, X 1OI 0,85 2,73 x 10'
N- - 1.90 6,1L x .101 1.77 5a70 :C a.0--
N•Averelalfe val uec for' v' 0: O id v' !levels or NO(A2F•)
I"P
27
-
Tho nitric OXr.io vibrationnl temapraturoes wore dotemmined from
theratio of' mnasfxod (1,5) tnd (0A•) band intensition. To cecount
for therelative seneitivitita of the lio ohann•els, the measuroed
ratios werescaled according to the ratio mo•suied i•n the static
teak chamber.Hence, the intensity ratio wan dtoermhied as
L~~L~47650 t~ (16)aI
where the subscripts I and II denote the intensities a-f
ahannels I andII, rospectively, mid 0.765 is the room-temperature
vibrational beandintensity ratio for channels with equal
sensitivities (Figure 1).
T!ho number densities of molaoitlar nitrogen. were determlIned
from
the measured intensitios of the (0,1) and (1,2) bhande of the
N?+ firstnegative system at 4278 A mnd 4236 A, respoctively. The
(0,1) bandintensity wan measured with channel I, while that for the
(1,2) bandwas measui'ed with channel. 11. Since a pre-rmn
calibration for eachchannel was easily possible by passing the
elactron beam tin ough thetunnel teat eabin tinder static pwIp-dm
conditions, the data .adklctio-nprocedures for the Nl measurements
were simpler than those for the NO
-till.. 14vnban err .4m ofi obtainead t'rom the measurd
b.AdisxeaUJtieu with the procedur• describ,,d in Re•. 1; that
is,
NN NJ(17)NN• WjW~7TI(1~7r
whore (NN2) is the N_2 n•u.ber donsity of the pro-ru)n
calibratlons. The
quenching factor was determIxed fProm the species ooneentrmaiona
obtalnedd-,rome the nonequilibrium cai'oulation with no iteration
on the individualspecies couientralions. The quencrhing densities,
•ý, for N. were
obtained frc•i Ref, 4 wad axe summarized in Table I.,
ph o 1, vibret tonal. te-po:.atnrreti were dete-;rhied fran the
mentasuredband intensities with the formula
LA. (Izl)h ,y.8•2 T)n 11 Y i (.8)
where 7.85 is the band intensity ratio for channels having
equl.sensiti.vities (Figure .).
28
-
To minimize the influences of run-to-run variations in the
datacorrelations, the measured number densities were
nondimensionalized bythe corresponding reservoir number densities.
The reservoir values[NOlo and [AN2o were determined from the
reservoir ccmposition obtainedfrom the average reservoir enthalpy
during the scan of the electronbeam.
V. RESULTS AND DISCUSSIONS
A. THEORETICAL ANALYSES
For comparison with the experimental results, the inviscid
flowIroi-erties at various stations in the EGF nozzles were
obtained with anozzle-flow computer program which is described in
Ref. 2. The programcomputes the numerical expansion of a reacting
gas mixture startingfrom an equilibrium reservoir through a
'streamtube of arbitrary geometry.The rotational and trmislational
degrees of freedom are assumed to beequilibrated throughout the
expansion. The vibrational energy mode canbe assumed to be either
in equilibrium with the translational energymode or frozen at the
reservoir condition. The electronic energy modeis assumed to be
equilibrated with the vibrational energy mode. Thec hemir yKr ,a
... .tz b ue " e reaecjoir state, remain inequilibrium, or to
proceed in a nonequilibrium fashion through theexpansion.
Corrections for the growth of the nozzle boundary layer areincluded
in the analysis.
B. NOMINAL RUN CONDITIONS
Wind tunnel data were obtained at three nominal run
conditions.The nozzle throat diameter was 0.4375 inch. For
conditions 2 and 3,the heater was operated at reservoir pressures
of 350 and 500 psiaand nominal enthalpies of 3500 and 2500 Btu/lb,
respectively. Forcondition 1, another arc heater was employed which
supplied a nominalenthalpy of 6000 Btu/lb with a reservoir pressure
of 250 psia.
The nominal reservoir conditions are summarized in Table III.
Therange of enthalpies (in Btu/lb) employed were 5599 to 5931 for
condition1, 2885 to 348o for condition 2, and two enthalpy ranges
for condition 3,2127-2301 and 3694-3936.
C. PROBE DATA
The pitot' pressure data are summarized in Figures 13.-17. It
shouldbe noted that little run-to-run variation in the pitot
pressure wasobtained.
29
-
TABLE III. NOMINAL REWERVOIR ACONDITION $UNMAMRYI
Run PO HO To
Condition (psia) (Btu/lb) (K)
1 2pO 6000 6564
2 350 3500 471A
3 500 2500 3973
2.0
OPEN SYMBOLS -ABOVE h1.6 SOLID SYMBOLS -BELOW ¢,.
RUN Ho(Btu/Ib)
0 46 28851.2 47 30
00 I 0 0
00S0.8U
00.4 O 0
0 _ _
0 2. 4 6 8 10
INCHES FROM TUNNEL _Figure 13. Pitot Pressure Surveys at Run
Condition 2;
19-Inch Nozzle; Po 350 psi&
30
-
OPEN SYMBOLS -ABOVE ..-
SOLiD SYMBOLS-BELOW _
i16 RUN Ho(Btu/Ib)0 49 2127
0 50 23050x 1.2-1
i0 F ) Re Do'•. .[]
00S0.8 -0H
00
0.4
0 I lI ...
0 2 4 6 8 10
INCHES FROM TUNNEL (.Figure 14. Pitot Pressure Surveys at Rmu.
Condition 3;
1.9-Inch Nozzle; Po 500 psia
31
-
0
> wwZ "-% t
w 0
•c t'- \
nr" > 0 cu ?"
O~~Oc
ooo W0 I I I I I 4-
a- o.1 1> 0 .r74
___ I I -o 'd
1 32
-
8.0
7.0 C i
AAV
6.0 V
05.0-
0 RUN Ho(Btu/Ib)0o 58 3,480).4.0 60 3420"le k "1.0961
a.OPEN SYMBOLS-ABOVE TUNNEL CL
3.0-- SOLID SYMBOLS- BELOW TUNNEL _
2~0
1.0-I.O_
O0 L__ 0I 2 302
INCHES FROM TUNNEL CL
FigLure 16. Pitot Pressture Surveys at Run Condition 2;7-Inch
Nozzle; po = 350 psia
33
| | | | | i i | !
-
8.0
Zoo&OV6.00
5.0
o 4.O RUN Ho(Btu/Ib)
0 63 21570 64 2129
3.0 0 65 3909L• 66 3936v 67 3694
2.0 OPEN SYMBOLS -ABOVE TUNNEL C
SOLID SYMBOLS- BELOW TUNNEL (L'
1.0
0. 0 1 2 3
INCHES FROM TUNNEL 6.
SFigure 17. Pitot Pressure Surveys at Run Condition 3;L• 7-Inch
Nozzle; Po = 500 psia
34
-
Axial surveys of the pitot pressures were taken to determine
thepitot pressure gradients throughout the region of measurement in
the7-inch nozzle. The data are summarized in Figures 3.8-21. The
axialvariations of pitot pressure shown in Figare 21 were used to
determinethe pitot pressures at the electron beam location to allow
accuratecomparisons of the experimental data with the restifts of
the theoreticalpredictions.
Similar axial surveys of pitot pressure in the 19-inch nozzle
arereported in Ref. 1, where it is showvan that the axial
variations arenegligible for all run conditions in the 19-inch
nozzle.
D. VIBRATIONAL TEMPERATUDES
The measured vibrational temperatures of molecular nitrogen
non-dimensionalized by the reservoir temperature are summarized for
the7-inch nozzle in Figure 22. Excellent run-to-run repeatability
wasobtained and little data scatter was observed.
The vibrational temperature ratio of approximately 0.A obtained
atrun conditions 1 and 3 is in agreement with vibrational
temperaturedata obtained in the 19-inch nozzle as reported in Ref.
1.
The- behavior of' the nitrogen vba~nltmeauedsrbtonear the
boundary layer edge is expected and indicates the tendency fora
greater degree of vibrational relaxation to occur ii the
low-speedportions of the flow field. Stiuiar effects were observed
in the19-inch nozzle., Note, howewer, at all run conditions there
i-s asizable degree of vibratiaial nonequilibrium.
The measured vl orational tempurat'n'es cf nitric oxide
nondimen-sionalized by the reservoir t ermttues ere siumuarized for
the 7-inchand 19.4ncb nozzles 5n Figures Ž3 and 24.
Vibratioial temperetare data could not be obtained for nitric
oxideat run -ondition 1, fox either nozzle, because of the
combination of anextrem(7y 1ow nitric oxide concentration and a
sizable background signal.Thit result is e:cpected, however;, since
estimates of 'the nitric oxideconcentrations at 'these -rn
conditions show that the nitric oxide partialpressure is leps than
0.0001 Torr. Since the low density limit for themeasurement
technique is near 0.001 Torr, the nitric oxide concentra-tions at
these run conditions are more than an order of magnitude belowthe
detectable limit. The measurement problem at rum condition I
iscourpounded by the background radiation which is approximately
twice asintense as those at rim conditions 2 and 3.
The sensitivities of the ratios of band intensities in the NO
ysystem place extreme requirements on the accuracy of 'the
intensitymeasurement system (Figure 1). For exaMple, for the
(i•5)/(O,Ž) bandcombination, an error in the measured ratio of ±1i%
will yield an error
35
-
0.8
. x=0.69 in.LO 0.6-
06
02 3
x-2,52 in.
x
Lo 0.6 VA!....
04
S0,46-0 2
o ! 2 3 :-
0.8
0.
R0. 6
INI
0 2 3INCHES FROM TUNNEL .
RUN Ho(Btu/ib) Po(psia)0 76 6055 251O 77 5416 252
OPEN SYMBOLS-ABOVE TUNNEL ,SOLID SYMBOLS--BELOW TUNNEL
Figure 18. Pitot Pressure Surveys at Various AxialStations - Rn
Condlition 1, 7-Inch Nozzle
361
-
x x=0.69 in.S0.6-
CL 0
0.4 Oj2 3
00xwX? 0.6 4,•, • ~x=2,52 in. •
o~,,)- IS S
0.4 .J!00 x4.34 in.
RUN__%o 78 3078 351F0 79 3755 354
OPEN SYMBOLS-ABOVE TUNNEL L-SOLID SYMBOLS-BELOW TUNNEL
Fi6're 19. Pitot Pressure Surveys at Various Axia.Stati-ons -
l,•u Condition 2, 7-Inch NozzleJ
237
-
0.84 x069 ir.
00• x= 2,58 in.
0. -0 I al
0.
0.4 ._ I
RUN Ho(Btu/Ib) Po(PSfo )0 80 2769 502(3 81 .3566 503
OPEN SYMBOLS -ABOVE TUNNEL •SOLID SYMBOLS -BELOW TUNNEL
F~i.g-e 20., Pitot 1-"•e~su're S~urveys at Varilous Axialdttons
- Run Condition 3,tt 7-Inchi No•,mz~l
38
C'A
-
pPPROBE ELECTRON
x 7 -
0 I 3 4
x, AA4A
0 I 2 13 4 6I!I I I
o I 2 3 4 5INCHES DOWNSTREAM OF NOZZLE EXIT
RUN Ho(Btu/Ib) Po(psio)o 76 6055 251o 77 5416 252'A 78 3078
351A79 3755 3540 80 2769 502
8 81 3566 503i,.ture 21. Axial CenterXine Mtot Pressures;
7-11ieh Nozzle
39
-
0.6
RUN CONDITION I
0I-
0.2-EQUILIBRIUM VIBRATION
0 2 3 40.6 ------- T .__
RUN CONDITION 3•o 0.4 - . . _.:,•,
------ EQUILIBRIUM VIBRATION
:0I0 ! 2 3 ,4
INCHES FROM TUNNEL
RUN COND RUN H (Btu/Ib) T0 ('1)10A I 74 5931 65290 i 75 5599
6346 40 ,3 64 21 29 3672o 3 65 3909 5131FLAGGED SYMBOLS- BELOW
-UNFLAGGED SYMBOLS --ABOVE t
Pigure 22. Np Vibrational Tenperatures;
74Inch Nozzle
40€ ., iN
-
00,8
0.6-
RUN CONDITION 20 •__W__.______L !0 1 2 3 4
0. . .... -r ...----i- -
RUN CONDITION 3
06 TQA *20%
0.2-
0 4 3INCHES FROM TUNNEL .
RUN COND RUN Ho(Stu/Ib) T0(0K)2 60 A, 4651
11 2 62 304,3 43603 66 3936 51553 67 3694 4944
FLAGGED SYMBOLS "BELOW (UNFLAGGED SYMBOLS-ABOVE 4.
Fiintule '23. -NOVi T rt e ;7-Inch Novzz~e
"h, i
-
I
O, -1RNCODTO 1.0.-RUN CONDITION a
0 2 4 6 8 I0O,
oAim
INCESFROM TUNNEL CLRUN COND RUN HO(BTu/Ib) T(J¶
o 2 46 288$ 42.5 1o 2 47 3029 43460 3 49 212" 4625
FLAGGED SYMBOLS- BELOW 9,UNFLAGGED SYMBOLS-ABOVE 9 A
Figxrue 21t. NO Vibractional Temperatur'es;19-Ilnel
No?0,z3.e
42
-
in vibrational temperature of ±25%. Hence, the accuracy of the
NO Ivibrational temperatures is estimated to be i±20%.
The scatter in the data of Figures 23 and 24 is generally
withinthe ±201/% accuracy expected for these measurements. The
averages of thenitric oxide vibrational temperatures fall into two
general categories:a vibrational temperature ratio near 0.4, and a
ratio near 0.25. Aclose coupling between the vibrational energy
modes of the variousspecies is expected due to the extremely rapid
vibration-vibrationenergy exchanges which occur. However, an
interesting trend in thehigner vibrational temperature data
obtained in the 19-inch nozzle isevident in Figure 24. These higher
temperature data show a definitetendency for the vibrational
temperatures to decrease near the edge ofthe boundary layer. These
variations may be related to the mechanismswhich lead to
chemiltuninescence caused by the reaction NO + 0 -- NO2 +
hv.Relatively strong radiation due to chemiluminescence has been
observedat various r~un conditions, 1 2 and it is likely that the
associatedchemical reaction will perturb 'the nitric oxide
vibrational populationdistribution.
The behavior of the ni'vric oxide vibrational temperature near
theboundary layer edge is in agreement with that obtained for the
molecularoxygen vibrational temperature variations. 2 However, the
changes inboth the molecular oxygen and nitric oxide vibrational
temperaturesnear the boundary layer edge are opposite to those
changes obtained forthe N2 vibrAtio•n' teýp + .... t iT s exected
that a greater degreeof vibrational relaxation will occur within
the lower-speed portionsof the boundary layer. Although the amount
of relaxation in the boundarylayer is small, decreases in the
vibrational tempera'tres are expectedrather than increases noted in
Figures 23 and 24. As discussed in Ref.2, these vibrational
temperature variations might result from a couplingbetween the
vibrational relaxation and the fast nitric oxide
shufflereactions.
E, NUMBER DENSITIES
The measured molecular nitrogen concentration profiles for
the7-inch nozzle are given in Figares 25 and 26. The theoretically
pre-dicted concentrations are also included.
The run-to-run repeatability and scatter within a given run
arewithin the ±10%1o accuracy expected for these measurements.
The nitrogen number density data obtained at run condition 1
withthe 7-,inch nozzle are in good agreement with the results of
the theo-retical pred Xtions.
The n- • .,en number density data obtained ab run condition 3 is
inpoor agreement, with the results of the theoretical predictions.
Itshould be noted that there is little scatter in the run-to-run
variations
43
-
10 0
103
RUN Ho(Btu/Ib) [N2]o (crf•-3
0
Z -4 A 74 5931 1.068X10 9 l"10 0 75 5599 1.130 x loll
"FLAGGED SYMBOLS-BELOW '• -- IJIl M¼•-- L"•,2k LI/ ' i ,vvt.jj.,
, -,.. '-... -
-THEORETICAL RESULTS FOR_ Ho= 5700 Btu/1b Po=250 psia-FROZEN
-" NONEQUILIBRIUM
- -- EQUILIBRIUM
L0 _____L_____0 I 2 3 4 5INCHES FROM TUNNEL Q_
Figure 25. NK Number Densities at Run Condition 1;7-Inch
Nozzle
-
-2210
0 RUN Ho(Btu/Ib [N2] 0 (cr-3 )
-- C 64 2129 4.99x10' 9-Z -4 .0 6 5 3908 3.II x I0'9
FLAGGED SYMBOLS - BELOW •.z UN"LA..ED SYMBOLS- ABOVE -
T THEORY AT Ho =3000 Btu/Ih, po=5 0 0 psia
FROZEN10 - -NONEQUILIBRIUM
EQUILIBRIUM
-0I J
0 I 2 4 5
INCHES FROM TUNNEL .
Figure 26. Na Number Densities at Run Condition 3;7-Inch
Nozzle
451
-
rP
and that the differences between the theoretical and
experimental re-sults are well outside the ±10% error band expected
for the data.
The experimental techniques give redundancy in the number
densitymeasurements. The number densities can be obtained either
from theintensities of the (o,i) or the (1,2) vibrational bands.
The numberdensities obtained from these two bands are coupled only
through thedensity correction factor, s(Tv), which must be obtained
from the vibra-tional temperature measurement. As seen in Figure 2,
-this coupling isrelatively weak. In all cases, the nitrogen number
densities obtainedfrom the two vibrational bands agreed with an
error less than ±2%.Hence, it is concluded that the differences
between the theoretical andexperimental predictions of the nitrogen
number densities are not aresult of systematic errors in the
measurement of the nitrogen concen-tration.
Many factors enter into the comparisons of the theoretical
andexperimental results. The data are nondimensionalized by the
reservoirnitrogen number densities, which are determined from
thermochemicalcalculations assuming complete equilibrium in the
reservoir. In addi-tion, the theoretical predictions are based on
the centerline pitotpressure values, while both axial and radial
pitot pressure variationsexist. The dLifferences between the
theoretical and experimental nitro-gen number densities may result
from cumulative errors in these factors.Note that there is little
variation in the predicted nitrogen nu.mberdensities due to changes
in the assumed chemical model, since molecularnitrogen behaves
almost as an inert chemical species in the temperaturerange of
these tests.
The measured nitric oxide species concentrations are compared
withthe results of the theoretical predictions in Figures 27-30.
Exceptfor the data obtained with the 19-inch nozzle at run
condition
(Figure 30), the measured number densities are consistently
below thepredicted values, indicating a greater degree of chemical
recombinationthan predicted by theory. Nitric oxide concentrations
resulting fromassuming chemically frozen and chemical
nonequilibrium only are includedin Figures 27-30. The theoretical
results assuming chemical equilibriumin the nozzle expansion give
nitric oxide concentrations less than2 X 10"5 Vol %
Generally, good run-to-run repeatability and little data
scatterwithin a given run were experienced with the nitric oxide
number densitymeasurements. The number densities shown in Figures
27-30 are those
obtained from the intensity of the NO y (0,2) band. The number
densitiesobtained from the NO y (1,5) band generally agreed with
those from the(0,2) band to within 8%.
The factors which affect the comparisons of the theoretical
andexperimental nitrogen densities also influence the comparisons
for thenitric oxide number densities. However, the consistency of
the differ-ences between the measured and predicted nitric oxide
concentrations
46
-
- I.
- - I
S~Ef
16-4
RUN H0 (Btti/Ib) [INOo] (cm 1)
-0 60 3420 3.00xIO 80 62 3049 3.36X 108FLAGGED SYMBOLS-
BELOW
10"5 --" UNFLAGGED SYMBOLS- ABOVE CLTHEORY AT Ho=30OOBtu/Ib,
po=350psia- -FROZEN
NONEQUILIBRIUM
()I2 3 4 5A
INCHES FROM TUNNEL ?
Figure 27. NO Number Densities at Run Condition 2;ib= 350 psia;
7-Inch Nozzle
47
-
Ilk-44
I --4_0 10 --
RUN Ho(Btu/Ib). [N 0o (cm"')
"0 66 3936 3.40x10'6
0 67 3694 3.90x1018_.Z FLAGGED SYMBOLS -BELOW (L
IV UNFLAGGED SYMBOLS-ABOVE -THEORY AT Ho=3800 Btu/Ib, po=500
psia
FROZENNONEQUILIBRIUM
I0"-s I I I I ... -
0 I 2 3 4 5
INCHES FROM TUNNEL C
Figure 28. NO Number Densities at Run Condition 3;Po = 500 psia;
7-Inch Nozzle
48
-
S-.
S." RUN H0(Btu/Ib)[N ocm3
3 47 3029 3.42 x10'
I0 FLAGGED SYMBOLS - BELOW CUNFLAGGED SYMBOLS - ABOVE CL
FROZENNONEQUILIBRIUM
-6IIi1. . .-'10
2 4 6 8 10
INCHES FROM TUNNEL CLFigure 29. NO Number Densities at Run
Condition 2;
Po = 350 psia; 19-Inch Nozzle
".9
-
-0 I0 .Ii I_=
0--4 RUN Ho(Btu/lb) [NO]o(cm"3) ---
o 0 49 2127 5.08x10-0 -FLAGGED SYMBOLS BELOW CLZ - UNFLAGGED
SYMBOLS ABOVE _L-
-THEORYAT Ho2t29 Btu/Ib, Po500 psi a
Z 10 -FROZENNONEQUILIBRIUM
0 2 4 6 8 i0
INCHES FROM TUNNEL (t
Figure 30. NO Nurber Densities at Run Condition 3;Po= 500 paia;
19-Irseh Nozzle
50
-
suggests that the reaction rates of one or more of the nitrio
oxideshuffle reactions should be changed to give an incroase In the
rate ofdisappearance of nitric oxide. Numerical experimentation
with the non-equilibrium flow computer program is required to
establish the apprc')ri-ate shuffle reaction rates. As discussed in
Section I, changes in theshuffle reaction rate onstants may have
important influences on 'thetheoretical predictions of the overall
properties of the test gas atthe nozzle exit.
Both the molecular nitrogen and nitric oxide species
concentrationsmeasured with the electron beam are influenced by the
rate of collisionquenching. The quenching densities xpplied in
these studies to relateband intensities to number densities were
obtained twn room-temperatureexperiments and no translational
and/or vibrational influences wereincluded. The collision quenching
of the N2 + first negative system at -*the run conditions for the
7-inch nozzle result in quenching factors,1 + ZNJI/Nj., near 1.5.
Hence, collision quenohing is an importantde-excitation mechanism
for the N2 + first negative system, and errorsin the quenching
cross sections could be responsible, in part, for thediscrepancies
between the theoretical and experimental number densities.
Quenching of the NO y7 system is much less severe than it is
forthe N2 + first negative system. For the conditions of the 7-inch
nozzletests, the quenching factor was less than 1.17. Hence,
collisionquenching of the NO y radiation was not a particularly
important factorin oonverting bead intensities -to iim-ber density.
However, the accuracyof the nitric oxide number density
measurements depends directly on theapplicability of the excitation
model proposed here. The relativeimportance of excitation by
secondary and primary electrons must bedetermined to obtain
accutrate nitric oxide number density data. Theintensities of the
NO y radiation, as a result of excitation by second-ary and primary
electrons, were determined from room-temperature experi-ments, and
it is possible that dtfferent excitation cross sections existat
elevated translational and vibrational temperatures.
511
-
!IV1. CONCLUSIONS
A. ELBOTION BEAM TIXAhftIIQUES
These studios have substantiated the applicability of the
highvoltage version of the electron beam generator for the 2-Foot
Flectro.geadynamios Facility, In addition, the applicability of the
diagnostictechniques for the measurement of the vibrational t%
erature and speciesconcentrations of nitric oxide have been
demonstrated. Operation of thebeam generator at high voltages (40
kV) leads to an increase win thespatial resolution in the
measurements becanue of the associated de-crease in elastic
scattering of beam electrons. The performance of thebeam generator
during these tests indicates that it could easily beused at. flow
densities greater than that corresponding to pressure of10 Torr at
a temperature of 300 X.
The utcertainties associated with the exoitation-eanission
processesfor N2,0, 0, 0a* and NO at high gas densities should be
investigated indetail. The relative influences of excitation by
secondary mid primaryelectrons should be examined under controlled
conditions of elevatedtranslational and vibrational temperatures.
The appropriate quenchingcross sections for these species must also
be known as functions oftranslational temperature, vibrational
temperature, and number densitybefore accurate electron beam data
can be obtained at high densities.
Determination of the upper density liuait for applicatiou of
theelectron beam technique is required before the fUll potential of
thetechnique can be realized. From a mechanical point of view, no
particu-lar difficulties in generating electron beams suitable for
higher densityflows are anticipated with the present beam generator
configuration.
B. TI•MOREICAL-E(PERIMFITAL COMPARISONS
The discrepancies between the theoretical, and experimental
nitrogennumber densities experienced in these studies were not
expected. It isunlikely that they result from deficiencies in the
nonequilibrium theorysince the chemical activity of molecular
nitrogen in these studies isquite low. The discrepancies probably
result fixon a combination offacility-related effects sad unknown
errors in the collision quenchingcross sections needed to convert
band intensities to nwmber density.
Comparisous between the theoretical and experimental nitric
oxidenumber densities indicate that the theory under-predicts the
rate ofdisappearance of nitric oxide within the nozzle expansion
process.Numericel experiments with the nonequilibrium flow
ocauputer program arerequired to establish shuffle reaction rates
which lead to better agree-ment between the theoretical and
experimental results.
52
---------
-
Additional experimental studies should be conducted to obtain
-temperatu-re and concentration data at enthalpy levels intenediate
be-tween those of rmu condition I wnd run conditionrs e. and 3ý The
resuli'sof these studies could then be employed effectively with
those fProm thenumerical experitents to isolate the apparent
recombination rates appli-cable to the expansion process. In
addition, the concentration andvibrational temperatture of
molecular oxygen and the concentration of.atcatc oxygen should be
determined at high densities to allow a morecomplete ecompaison of
the theoretical and exerimental results, Inal cases, these studies
should be performed with the Intent, of. develop-ing a theoretical
model for the expansion process which is usetu, for
predicting tunnel calibration data that cannot be measured
directly.
53
-
-•!
1. Petrie, 8, L., Boia'ski, A. A. and Lee, H, F., "Electron Beam
1F'lowField Arwayaes in the AFtDL Two-Foot Eloatrogasdyrnwiii
Faaftkity)"AFFDL-TR-71-161. (1971).
2. Pebrie) S. L. •nd KoMOa' J J 4 . "Eleoctron Beam Analysis of
thePr'ope1•tieo of boleo•cx wnd Atomio O>,Wgen in the AFIFL
2-FootElecyro6,ýasdynlmioio Facility," AFFDL-TR-73-10 (3.973),
3. Petrie, S. L. and Koem&r, J. J., "Applicabion of the
Electron Be=niFluorescence Technique to the Measurement of the
Properties ofNitric Oidae in Nonequilibrilm Flows," AFFDL-TR-72-lhh
(1972).
4, Mwitz, E. P., "The Electron Beam Fluorescenne Teclhique,"
AGAM)-graph 132, (Dec. 1968).
5. Petrie) S. T-,ý Pieree, G. A. &nd Fishburne, B. S.,
"mialysis ofthe Therniochehica.1 State ot mi Expanded Ail, Plarac,"
U. S. AirForce Flight Dynamics Laboratory Rept. AFFDL-TR-64-191
(1965).
6, Petrie, S. L., "Flow Field Analyses in a Low Density
Axc-Heated oWind Tnnel.," Poo lngof the 65 Heat Trkf.uisfor and
Fluid"Mech"aAnics e'ttlot, Stanford Unmiv. 7( of
7. Sobaciehr, D. 1. a nd Duckett' ]I. J . "A Spectrographic Pan
I•ito ofa 1-Foot Hypersonic-Arc-Tiniona., krstream Using an
rleotron BeamProbe " NASA TR R- (3.94).
8. Petrie) S. L., et al., "Electron Benm Studies of the
PropertieA ofMolecular and Atomic Oxygen," AFFDL-TR-71-30
(.971).
9. Pearse, R. W. B., and Gaydon, A. G., The Edentific&tion
of Molecular'SEcta, Chalvmann told Hall Ltd., Iondond•T •S}
10. Parobek, D. M., "Performance of Freestrean Flow
3istrutuentaticon for9-Inch Contoured Nozzle Tests in the 1aD
11-Mcgawatt Elctrog dynamicFacility," U, S. Air Force Fl:ight
Dynan0d.cs Labor&m•ovx Rept. IAFtIL-TR-65-2.79 (1965).
11. Melton, L. A. and Klemperer, W., PELa.et. Space Sod, 20, 157
(1972),
12. Maitrup, P. N. and Herrett, 1R. 11., "Opt-ical Scattering
Diagnos-ticTechniques for llyl)ersonic A•c Flows," AF1DL-TR-T71I4.
(1971).).
[~514