Experimental Studies of High-speed Liquid Films on Downward ...
Hydrodynamics of Liquid Protection schemes for IFE Reactor Chambers S. I. Abdel-Khalik and M. Yoda IAEA Meeting - Vienna (November 2003) G. W. Woodruff School of Mechanical Engineering Atlanta, GA 303320405 USA OUTLINE Introduction Problem Definition Description of Liquid Protection Concept The Wetted Wall Concept Numerical Studies Experimental Verification Forced Liquid Film Concept Thick Oscillating Slab Jets (HYLIFE) Concept 2 Wetted Wall Concept--Problem Definition Prometheus: 0.5 mm thick layer of liquid lead injected normally through porous SiC structure
Liquid Injection ~5m First Wall X-rays and Ions 3 Forced Film Concept -- Problem Definition Prometheus: Few mm thick Pb forced film injected tangentially at >7 m/s over upper endcap ~5m X-rays and Ions Injection Point First Wall Detachment Distance xd
Forced Film 4 Turbulent Liquid Sheets HYLIFE-II: Use slab jets or liquid sheets to shield IFE chamber first walls from neutrons, X-rays and charged particles. Oscillating sheets create protective pocket to shield chamber side walls of stationary sheets (or cylindrical jets) shield front/back walls Lattice while allowing beam propagation and target injection Beam-tube vortices Cylindrical jets Pictures courtesy P.F. Peterson, UCB Oscillating slabs 5 Thin Liquid Protection Major Design Questions a stable liquid film be maintained over the entire surface Can of the reactor cavity?
the film be re-established over the entire cavity surface Can prior to the next target explosion? a minimum film thickness be maintained to provide Can adequate protection over subsequent target explosions? Study wetted wall/forced film concepts over worst case of downward-facing surfaces 6 Numerical Simulation of Porous Wetted Walls Summary of Results Quantify effects of velocity w injection film thickness z initial perturbation geometry & mode number Initial angle inclination Evaporation & Condensation at the interface in
o on detachment time Droplet droplet diameter Equivalent Minimum film thickness prior to detachment Obtain Generalized Charts for dependent variables as functions of the Governing non-dimensional parameters 7 Numerical Simulation of Porous Wetted Walls Effect of Evaporation/Condensation at Interface z =0.1, w o * in * =0.01, Re=2000
mf+=-0.005 (Evaporation) *=31.35 mf+=0.0 *=27.69 mf+=0.01 (Condensation ) *=25.90 8 Numerical Simulation of Porous Wetted Walls Wetted Wall Parameters Length, velocity, and time scales : l / g (L G ) U o g l Nondimensional minimum film thickness :
Nondimensional initial film thickness : Nondimensional injection velocity : Nondimensional drop detachment time : to l / U o * td / to *min min / l * o z zo / l win* win / U o 9 Experimental Validations 1 Flow Flexible tubing 2 Reservoir level 3 8
4 7 6 1 2 3 4 5 6 7 8 9 10 11 Constant-head supply tank w/var. height Perforated tube Shut off valve Test section porous plate, 316L SS Sump pump Sub-micron filter Fast stirrer Unistrut frame Air relief valve Baffles
Unperturbed film thickness, z Dependent Variables time Detachment diameter Detachment Maximum penetration depth in o 11 Penetration Depth [mm] Experiment #W090 -Evolution of Maximum Penetration Distance Experiment Simulation Time [sec] 12 Wetted Wall Summary general non-dimensional charts applicable to
Developed a wide variety of candidate coolants and operating conditions of liquid film imposes Stability Lower bound on repetition rate (or upper bound on time between shots) to avoid liquid dripping into reactor cavity between shots Lower bound on liquid injection velocity to maintain minimum film thickness over entire reactor cavity required to provide adequate protection over subsequent fusion events Predictions are closely matched by Experimental Model Data 13 Forced Film Concept -- Problem Definition Prometheus: Few mm thick Pb forced film injected tangentially at >7 m/s over upper endcap ~5m
X-rays and Ions Injection Point First Wall Detachment Distance xd Forced Film 14 Forced Film Parameters U 2 We
Weber number We Liquid density Liquid-gas surface tension Initial film thickness Average injection speed U Froude number Fr U Fr g (cos ) Surface orientation ( = 0 horizontal surface) Contact Angle, LS Mean detachment length from injection point xd Glass : 25o Mean lateral extent W
Coated Glass : 85o Surface radius of curvature R = 5 m Stainless Steel : 50o Surface wettability: liquid-solid contact angle LS Plexiglas : 75o In Prometheus: for = 0 45, Fr = 100 680 over nonwetting surface (LS = 90) 15 Experimental Apparatus A Flat or Curved plate (1.52 0.40 m) B Liquid film C Splash guard D Trough (1250 L) E Pump inlet w/ filter F Pump G Flowmeter H Flow metering valve I Long-radius elbow J Flexible connector
K Flow straightener L Film nozzle M Support frame L I J K z H x M A B gcos G Adjustable angle
g C F E D 16 Experimental Parameters Variables Independent Film nozzle exit dimension = 0.10.2 cm Film nozzle exit average speed U0 = 1.9 11.4 m/s Jet injection angle = 0, 10, 30 and 45o Surface inclination angle ( = ) Surface curvature (flat or 5m radius) Surface material (wettability)
Dependent Variables Film width and thickness W(x), t(x) Detachment distance xd Location for drop formation on free surface 17 Detachment Distance 1 mm nozzle 8 GPM 10.1 m/s 10 inclination Re = 9200 18 Detachment Distance Vs. Weber Number 160 = 0 = 1 mm 140
We 19 Penetrations and Beam Ports obstructions modeling protective dams around Cylindrical penetrations and beam ports incompatible with forced films Film either detaches from, or flows over, dam y y x y x x 20 Forced Film Summary windows for streamwise (longitudinal) spacing Design of injection/coolant removal slots to maintain attached protective film
Detachment length increases w/Weber and Froude numbers chamber first wall surface requires fewer Wetting injection slots than nonwetting surface wetting surface more desirable protective dams around chamber Cylindrical penetrations incompatible with effective forced film protection Hydrodynamically tailored protective dam shapes may also fail 21 Turbulent Liquid Sheets HYLIFE-II: Use slab jets or liquid sheets to shield IFE chamber first walls from neutrons, X-rays and charged particles. Oscillating sheets create protective pocket to shield chamber side walls of stationary sheets (or cylindrical jets) shield front/back walls Lattice while allowing beam propagation and target injection Beam-tube vortices Cylindrical
jets Pictures courtesy P.F. Peterson, UCB Oscillating slabs 22 Thick Liquid Protection Major Design Questions it possible to create smooth prototypical turbulent liquid Issheets? 5 mm clearance between driver beam, sheet free surface in protective lattice > 30 year lifetime for final focus magnets adjacent sheets, once they collide, separate and re-establish Can themselves before the next fusion event? the flow be re-established prior to the next fusion event? Can Chamber clearing Hydrodynamic source term Beam propagation requirements 23 Flow Loop Pump-driven recirculating flow loop Test section height ~1 m
Overall height ~5.5 m A C E F H J Pump Flow meter Flow straightener Nozzle Sheet Butterfly valve B D Bypass line Pressure gage G I K Oscillator (Not used) 400 gal tank
700 gal tank 24 Flow Conditioning inlet (12.7 cm ID) to rectangular Round cross-section 10 cm 3 cm (y z) 3.8 cm Perforated plate (PP) PP HC FS 3 cm 14.6 cm Open area ratio 50% with staggered 4.8 mm dia. holes (HC) Honeycomb 3.2 mm dia. 25.4 mm staggered circular cells mesh screen (FS)
Fine Open area ratio 37.1% 0.33 mm dia. wires woven w/ open cell width of 0.51 mm (mesh size 30 30) contracting nozzle 5 order Contraction ratio = 3 Note: No BL trimming th z x y 25 Experimental Parameters = 1 cm; aspect ratio AR = 10 number Re = 130,000 [U average speed; Reynolds liquid kinematic viscosity] number We = 19,000 [ liquid density; Weber surface tension]
Froude number Fr = 1,400 Fluid density ratio / = 850 [ gas density] z Near-field: x / 25 o L L G G x y 26
Surface Ripple Measurements surface interface between fluorescing Free water and air Planar laser-induced fluorescence (PLIF) = standard deviation of free surface zFree surface found w/edge detection Threshold individual images y Nozzle x Light sheet z position spatially averaged over central 7.5 cm of flow z g CCD
1 cm z x y Original image Image after thresholding, edge detection 27 Surface Ripple: Nozzle H 0.06 measure of z average surface ripple z x / < 25 z / / < 4.3% for
0.04 0.02 essentially z Re = 25,000 50,000 independent of Re 97,000 0 z slightly as x 0 10 x / 20
30 28 Turbulent Breakup Flow Nozzle xi primary breakup Turbulent Formation of droplets along free surface: hydrodynamic source term Due to vorticity imparted at nozzle exit of breakup, x Onset Location of first observable i droplets xi as Weber number We
29 RPD-2002 Correlation Results [Sallam, Dai, & Faeth 2002] droplet mass ejection rate 1300 kg/s Total Assumes G(x = 1 m) over entire surface area of each respective jet (Mean value of predictions) ~3% of total jet mass flow rate mean dia. 5.7 mm for all jets at x = 1 m Sauter SMD at x 0.82 1.0 mm for d = 4.61 i 15.6 cm, respectively 30 Beam Propagation Implications predictions imply protection concept is Model incompatible with beam propagation requirements model is based on : However,
Fully developed turbulent pipe flow at exit No flow conditioning, nozzle or BL cutting nozzles / jets be designed to reduce these Can number densities to a level compatible with beam propagation requirements? 33 Boundary Layer Cutter (remove BL fluid) Cut on one side of liquid sheet control: Independently Cut depth, zcut Downstream location of cut, x liquid (~0.18 kg/ Removed s) diverted to side 34
Cutter Details blade inserted Aluminum into flow 7.5 mm Nozzle zcut Diverted (cut) fluid Cutter blade Remove high vorticity / low momentum fluid near nozzle wall Blade face tilted 0.4 from vertical Blade width (y-extent) 12 cm short Relatively reattachment length
Nozzle contraction length 63 mm 35 Mass Collection Procedure y z 1 2 3 45 opening = 1 cm 1 Cuvette cm w/0.9 mm wall thickness Five adjacent cuvettes Cuvette #3 centered at y = 0 x at x, z away from
Located nominal jet position s 6.5 zs 2.515 mm Experiments repeated to determine uncertainty in data zs Cuvettes Mass collected over 0.51 hr 36 Experimental Number Density Equivalent average number density, N (# / m3) (x / = 25) 2.0E+21 Standard Design No Fine Mesh Closed No cutting
Open 0.25 mm cut 1.5E+21 1.0E+21 5.0E+20 0.0E+00 0 5 10 15 Cuvette standoff distance, zs (mm) 20 37 Summary: Mass Collection straightening and contracting nozzle Flow significantly reduce ejected droplet mass (by 35 orders of magnitude) compared w/model cutting has considerable impact on collected BL
droplet mass BUT: proper flow conditioning more important conditioning and BL cutting reduce collected Flow droplet mass by orders of magnitude (compared with model predictions) 38 Conclusions source term sensitive to initial Hydrodynamic conditions geometry, surface ripple and breakup affected by Jet flow conditioning conditioning / converging nozzle reduces droplet Flow mass flux (and number density) by 35 orders of magnitude over model predictions cutting appears to eliminate droplet ejection for a BL well-conditioned jet Preventing blockage of fine mesh screens major issue 39
Acknowledgements Georgia Tech Faculty : Damir Juric and Minami Yoda Academic Faculty : D. Sadowski and S. Shin Research : F. Abdelall, J. Anderson, J. Collins, S. Durbin, L. Elwell, T. Students Koehler, J. Reperant and B. Shellabarger DOE W. Dove, G. Nardella, A. Opdenaker ARIES-IFE Team LLNL/ICREST W. Meier, R. Moir 40
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