A Design Tool for Aerodynamic Lens Systems - Department of ...
A Design Tool for Aerodynamic Lens Systems - Department of ...
A Design Tool for Aerodynamic Lens Systems - Department of ...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
A DESIGN TOOL FOR AERODYNAMIC LENS SYSTEMS 333<br />
p1<br />
pressure upstream <strong>of</strong> an orifice<br />
p2<br />
fully recovered pressure downstream <strong>of</strong><br />
an orifice<br />
pfocusing<br />
pressure upstream <strong>of</strong> a lens <strong>for</strong> focusing<br />
particles <strong>of</strong> a given size<br />
pMa<br />
minimum pressure <strong>for</strong> flow to be subsonic<br />
pmax<br />
maximum operating pressure <strong>of</strong> an aerodynamic<br />
lens<br />
pKn<br />
minimum pressure <strong>for</strong> flow to be continuum<br />
Q volumetric flowrate<br />
Qi<br />
volumetric flowrate at stage i<br />
R universal gas constant<br />
Re flow Reynolds number based on orifice<br />
diameter<br />
Res<br />
flow Reynolds number based on spacer<br />
diameter<br />
ri<br />
critical initial particle radial position<br />
r pi<br />
particle initial radial location in an aerodynamic<br />
lens<br />
S Sutherland constant<br />
Sa<br />
particle axial stopping distance<br />
Sr<br />
particle radial stopping distance<br />
St Stokes number based on orifice diameter<br />
Sto<br />
Sts<br />
Sts50<br />
optimum Stokes number<br />
Stokes number based on spacer diameter<br />
Spacer Stokes number corresponding to<br />
a 50% impaction loss<br />
stage i includes lens i and the downstream<br />
spacer<br />
t<br />
T1<br />
TpF<br />
particle residence time<br />
temperate upstream <strong>of</strong> the lens<br />
particle frozen temperature in the jet expansion<br />
Tr<br />
u<br />
reference temperature in Sutherland’s<br />
Law<br />
average flow velocity at orifice entrance<br />
based on upstream flow conditions<br />
u p<br />
particle axial velocity<br />
Us<br />
va<br />
vpr<br />
average flow velocity in the spacer<br />
axial jet flow velocity<br />
particle terminal radial velocity in the<br />
vacuum chamber<br />
vr<br />
xc ≈ 1 −<br />
radial jet flow velocity<br />
� �p pressure drop across an orifice<br />
ηc<br />
particle contraction factor<br />
ηc,i<br />
contraction factor at lens i<br />
ηt<br />
particle transmission efficiency<br />
ηt, diffusion, i penetration after diffusional loss at stage<br />
i<br />
ηt, GK, i<br />
penetration after loss at stage i estimated<br />
by Gormley-Kennedy equation<br />
ηt, orifice, i<br />
transmission efficiency after impaction<br />
losses on the orifice plate i<br />
ηt, spacer, i<br />
transmission efficiency after impaction<br />
loss to spacer i<br />
θ jet opening angle<br />
λ1<br />
mean free path <strong>of</strong> the gas molecules upstream<br />
<strong>of</strong> the orifice<br />
µ carrier gas viscosity<br />
ξ =<br />
� γ<br />
2 γ −1<br />
γ +1<br />
xrms<br />
particle root mean square displacement<br />
due to diffusion<br />
xrms,i<br />
root mean square displacement between<br />
lenses i and i+1<br />
Y<br />
β = d f /ds<br />
γ<br />
orifice flow expansion factor<br />
constriction ratio<br />
specific heat ratio <strong>of</strong> the carrier gas<br />
Dils,i<br />
Qi<br />
dimensionless diffusion deposition parameter<br />
ρ1<br />
carrier gas density upstream <strong>of</strong> the aerodynamic<br />
lens<br />
ρp<br />
particle material density<br />
τ particle relaxation time<br />
REFERENCES<br />
Back, L. H., and Roschke, E. J. (1972). Shear-Layer Flow Regimes and Wave<br />
Instabilities and Reattachment Lengths Downstream <strong>of</strong> an Abrupt Circular<br />
Channel Expansion, J. App. Mech. 94:677–681.<br />
Bean, H. S. (1971). Fluid Meters: Their Theory and Applications (Report <strong>of</strong><br />
ASME research committee on fluid meters). New York, ASME.<br />
Cheng, Y. S., and Dahneke, B. E. (1979). Properties <strong>of</strong> Continuum Source Particle<br />
Beam. II. Beams Generated in Capillary Expansions, J. Aerosol Sci.<br />
10:363–368.<br />
Dahneke, B. E., and Cheng, Y. S. (1979). Properties <strong>of</strong> Continuum Source<br />
Particle Beam. I. Calculation Methods and Results, J. Aerosol Sci. 10:257–<br />
274.<br />
Di Fonzo, F., Gidwani, A., Fan, M. H., Neumann, A., Iordanoglou, D. I.,<br />
Heberlein, J. V. R., McMurry, P. H., Girshick, S. L., Tymiak, N., Gerberich,<br />
W. W., and Rao, N. P. (2000). Focused Nanoparticle-Beam Deposition <strong>of</strong><br />
Patterned Microstructures, Appl. Phys. Lett. 77(6):910–912.<br />
Dong, Y., Bapat, A., Hilchie, S., Kortshagen, U., and Campbell, S. A. (2004).<br />
Generation <strong>of</strong> Nano-Sized Free Standing Single Crystal Silicon Particles,<br />
J. Vacuum Sci. & Technol. B: Microelectronics and Nanometer Structures<br />
22(4):1923–1930.<br />
Drewnick, F., Hings, S. S., DeCarlo, P., Jayne, J. T., Gonin, M., Fuhrer, K.,<br />
Weimer, S., Jimenez, J. L., Demerjian, K. L., Borrmann, S., and Worsnop, D.<br />
R. (2005). A New Time-<strong>of</strong>-Flight Aerosol Mass Spectrometer(TOF-AMS)—<br />
Instrument Description and First Field Deployment, Aerosol Sci. Technol.<br />
39(7):637–658.<br />
Eichler, T., de Juan, L., and Fernández de la Mora, J. (1998). Improvement <strong>of</strong><br />
the Resolution <strong>of</strong> TSI’s 3071 DMA via Redesigned Sheath Air and Aerosol<br />
Inlets, Aerosol Sci. Technol. 29(1):39–49.<br />
Fernández de la Mora, J., and Riesco-Chueca, P. (1988). <strong>Aerodynamic</strong> Focusing<br />
<strong>of</strong> Particles in a Carrier Gas, J. Fluid Mech. 195:1–21.<br />
Fernández de la Mora, J., Rosell-Llompart, J., and Riesco-Chueca, P. (1989).<br />
<strong>Aerodynamic</strong> Focusing <strong>of</strong> Particles and Molecules in Seeded Supersonic Jets.<br />
in Rarefied Gas Dynamics: Physical Phenomena, Progress in Astronautics &<br />
Aeronautics. E. P. Muntz, D. P. Weaver, and D. H. Campbell, eds., Washington,<br />
DC, AIAA. 117:247–277.