Feasibility study of ring-vortex gaseous-core cavity reacto

Chang, C. C.

English

NASA Technical Reports Server

THE CATHOLK: UNNEFlStlY OF AMEIUCA 
Washington, D. C. 20017 
Cmtroct No- NsG 586 
Submitted to: 
Office of Gmntt and lbsewch Contmcb 
WdtngtOn,D.C. 
Nationol AeroJIGlticr and Space Ahtnistrotlon 
https://ntrs.nasa.gov/search.jsp?R=19660028025 2020-03-16T17:35:38+00:00Z
f f . 
-2- I 
'. nd wafi . In h i s  case, the flow pattern in the side v iew i s  shown in Fig. 1 a d i s  
cfained thr .# i : jh  Tterpretation from many photographs an j  observations with i jection of 
w r e z c e n j  ., * L  sc;ir:ion intr> t he  water ffo,v in the cylindrical cavity. Tile dktrihulion of 
: Y-cirtctron ? F  
c f  velocity ccmponents, tl (radiau \f (tangentid) and V i  (axial), o t  tbr:e sect ons, 
I .. 2, and 3, These distributions are interpreted from the Aye quaiitativelymd are not 
e~ rcurofe enough but consistent with the flow pattern observed. The static pressuret at 
s-ztions 0 and 4 are also indicated. The detail description wi l l  not be iiven hew and 
L, 
L vity ?eacrcr ?V.todeI, " which i s  in progress ond wil l  be published later. 
a l m ~  t h G  cytinler axis i s  also indicute.1. Fig. 2 stmvsdw l i s i  ihutiow 
be included in  a report entifled, "End Wall Effect on Flow Pattern of Cyl indr id  
I "  
T1-e aFpcrent advantages of the square step end wolfs are the followirlg: 
0) Bottom sqLcIre step end (outlet side) cut-off the end second f l o w n  much that leak 
i s  extremely srrlalf and that the boundary secondary flow becomes exttemly thin. 
(ii} A recircv!cition zone i s  formed between the zone of center farjovir3 jownward 
ffow an1 h e  u ~ w c r i  wall f low zone. The foner may be called core flcw LO* and the 
faiter upwari flow zone. The total discharge of core flow i s  nearly constant in amount and 
i n  size at any section below the top tip of the recirculafion zone. In this z~ne  of recirculdm, 
Tclow i s  nearly two-dimensional vortex motion while both U and W are txtremely small. 
Therefore, the trapped water of flourescent dye can recirculate around, difft,se very slowly 
and last a very long time. The apposite moving fluid on both sides of the r e  irculation zone 
w:ll not encounter each other and the velocity gradient i s  very small inside *he recirculation 
zone. The tcngLntial velocity V in the recirculation Lone varies nearly ,tith 1 and is 
nearly potential Thus, the viscous loss can t.-e neglected. Maximum tanyentiol velocity 
i , -ely occurs in this zone 2nd the strong centrifugal force can trap heavy !'hid. Tr4erefore 
- 
r 
1 . 5  
.. 1 
-3- 
gtood confaainrnent of heavy fluid can ,e obtained. ..I this zone, the invicid flow theuy con 
Le applied. 
(iii) In the uyvard ffow zone, all the incoming fluid flows spirally upward and inward 
oiong helixicai path and passes around the top of the said recirculation zme and concentrcrtes 
radially inward to join the downward core flow. 
tP 
(iv) The flow field in cylindrical cavity is,divided into f ive zones: (a) core flow zone 
of nearly constant (b) recirculation zone mainly a region of a potential 
vortlx, (c) upward flow zone, rising spiral ffow which increases nearly linearly with height 
5rsmkottorn waft, (d) top secondary flow zone which is a thicker layer and (e) bottom secondary 
? b , v  zone which i s  extremely thin layer. Fig. 2 shows clearly the zones of (a), (b) and (c). 
&w$-d.l.ec". 
(v) Gap between each end step and,,wall a c t s  os a cushion to reduce the hear s t m s  and 
aflows the decay of circulation very slowly. This reduces the viscous dissipation. The centri- 
fugal force of reasonably large rotational velocity in  the gap can blonce against the radial 
pressure grafient, and i s  favorable to reduce the secondary flow in the gap. The static pressure 
Jictributions both near the top and bottom are,shown in Fig. 2 
@ 
(vi) Any transient change in the flow rate in the zone of recirculation w i l l  change the 
size of the zone immediately. If the flow rate increases suddenly, the recirculation zone 
Doves inward into the core flow, and the trapped flourexent fluid i s  quickly washed away 
by the core fiow. if the flow rate decreases, the recirculation zone wilf expand beyond the 
step and again she trapped flwrescent fluid is washed away by the upward outer flow. Thus, 
the trapped dye solution in  the recirculation zone loses very quickly. 
Curve3 Step - Seems to increase secondary flow loss at the top and to increase the loss of 
the core flow. 
i " t f  . 
Tapered Outward Steps - Produced pr4p trdnsient, boonlfory interface between the recircuiation 
zone and outer upward flow zone. Therefore more diffusion losses occur. It i s  expected to 
I * ’  . -4- 
’:E p ~ r  in  ~02ttdi.rrn~nt of hemy fluid. 
F!st V h f i  Yc~i-!; No Steps - This arrangement seems to produce more complex flow pattern 
;:CJ the gemotry with square steps. Secondav flows both in the top and bottom layer 
r e r i m s  are stmnger omf loss is  more- The recirculation zone i s  always small and the peak 
3f maximum tangmtial  velocity is sharper, and diffusion i s  s h n g .  The conbinment i s  
-- 
definitely inferior to tha, of the square step case. I 
(b) Heavy and Light G a s  Mixture 
The model is opraied with a fixed ratio of heavy and light gas mixture (Freon 
cnJ hefiurn) under choking condition at the outlet throat. It is planned to measure the 
composition of $as mixture continously with time at the throat at outfet which i s  in high 
vcxuurn. Afier running for a sufficiently long time until the exhaust mixture approaches 
closely to the fixed inlet mixture, the cylindrical cavity is stopped and isolated and mixture 
composition in  the caviiy i s  determined. The work is in progress and w i l l  be reported later. 
(5) Toroidal Geometry 
The great advantage of toroidal geometry i s  the fluid vortex ring which has no open 
Ends, Therefore, the secondary flow loss con be eliminated. With centrifugal effect, in 
c r i e r  to keep the heavy gas or particles of the inner diameter of the ring as far fr0;n the 
outlet mouth as possible, strong rotation along the  ring direction is essential. Thus, the 
fliuid particle moves helexically along the ring. Now near the outlet, the pressure i s  very 
fsw and the %w direction i s  reversed and the flow wil l  expand and be choked there. The 
rotating lighter gas wilf expand suddenly and will be able  to turn around the sharp corner to 
escape through the nozzie to vacuum. This phenomenon is somewhat sirnilcr to Prandtl-Meyer 
flow but much more complex because of the three-dimensional rotational flow, The heavy 
gas being of higher density wi l l  expand much slower in response to pressure than the lighter 
-5- 
i' - me. tt i s  expcted that the heavy gas being of higher momentum moves fast but cannot 
:,:m so large an angle of 90 as the light one. Tberefore, the heavy gas cannot expand 
d 
0 
h enough to enter the nozzle throat ko escape, but strikes on the surface of the sharp 
c m e  of the center of the cavity bottom tangentially and remains to recirculate i n  the 
ccvit.j. Let ss consider the operating cyde of the propelfant, The cold light gas4injectecl 
k m  tho waif into the cavity, diffused into hecwy fuel gas, absorbs the heokand rotates with 
i-he ring vortex fiow and escapes by turning around a sharp comer into the vacuum of outlet  
&A 
-
zszzie. Beceuse of the fow pressure near tfii nozzle throat, the fight gas will accelerate 
--<e, :::\,rc thcn the I~cwy one and more easily turns around the sharp comer.  At the inner radius 
3,; the ring cavity, the horizontal tangential velocity component i s  the highest and the out- 
ward centrifugal Force is highest. merefore, heavy gas can separate from the wall before 
reaching the mouth of the nozzle. This desirable phenomena can happen only when inward 
centrifugal force of the vertical tangential component, plus the pressure gradient, is much 
smaller than the outward centrihugal force due to h0t;zontaI tangential velocity component. 
There are many advantages of the toroidol ~eOmetrY: 
a) No secondary flow loss i s  possible because of no ends. 
b) The horizontal tangentiat velocity component and the vertical tangential 
velocity component can &e controlled mpamtely to meet the flexibility af reactor ioading . 
c) The suction at the nozzle mouth can occelerate the gas flow to nearly sonic 
speed within the cavity. Higher outward centrifogal force c a n  separate the heavy gas 
better if the horizontal tangentiol velocity i s  high enovgh. 
d) The reverse flow nozzle can ptevent the heavy gas from turning more than 5Qo 
and from escaping. 
. *  . 
b e) Pressure diffbsion i s  a function of temperature. %e lower temperature 
crmzicted xf:!: suction near the outlet will reduce the pressure diffirsiuri also. This i s  
SQ far tfre foroidaI model is operated with (a) water and &XSS buds, (b) gas and 
i5cmrescent solid particles of sawdust. The containment i s  excellent. With the available 
experimental the wafer speed is too low to give good containment with oil droplets a 
OF gas rnixhtres. Also the flow i s  too turbulent and the oil droplets are too fine. A great 
&el of si-udy ond rerSnement i s  needed before the flow patnem and pressure distribution 
e m  h ijtferpreted qualitatively with confidence. 
(C) Tvm-Di;r,ensioncl Improvement on Lewis Coaxial Com Reactor 
A two-dimensional model with recirculation cavity of gaseous nuclear fuel is 
developed. ARer muny odivt)merrts and improvements, the nrojel con keep he fuel much 
longer than the previous mmjeI. However, the work is in the preliminmy st.qle and fwther 
study should be done. 
fli. Theoretical V h r k  
(A) Cyfindricd Geometry 
fa) Aooroxirnote Analysis 
Owing to corapltcated gemmetry of tke scpcwe step cylindrical model, exact 
theoretical analysis i s  not possible for the immediate future. Some approximate analysis 
is carried out with given boundary conditions such as 
(1) ike cylindrical wall with assuming axial symmetry wo = 0 # b 
and Vo are given constan&. 
and unsieady when the Reynolds number becanes large. Hence, tb p m b b  has to 'JO 
ment of the end wull boundary layer flow and rhs viscous e x  cotme 

profiles. Tbis &tom will be tnvestigated In the w futurcr. 
. .  
few &e 0p)ically thick mglre. The thl~knssf o radiation layers i s  also calculated, 
-11 - 
(E) Qubliccrtiant 
The reports are shown in the following If* 
65-00'1 T ,  Kca, 
65-003 T. Errkt 
. 
1)* 
65-006 H. Pa0 
66002 
66007 
6641 1 
Y.C.- 
T. fib 
Y.C.- 
T. Eislsr 
-12 - 
NASA CR330 
Aut& 
9, 6, Juris 1966 
phvtkt of Ruidt, 
9, 4 June 1966 
To appmr in AIP 
1966 
Jarmcri, sept. 
I! 
70 
0 
C 
-5- 
b z 
3 
C 
A d 


A Fundamental and Feasibility Study of Ring- Vortex Gaseous-core Cavity Reactor Fifth Semiannual Report, 1 Feb. - 31 Jul. 1966

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server