Design and Evaluation of a New Aerodynamic Lens for the Aerodyne AMS

Leah R. Williams, John T. Jayne, Kori Moore*, Jenny McInnis**, Tim Onasch, Manjula Canagaratna and Douglas R. Worsnop

Aerodyne Research, Inc., Billerica, MA

Rensheng Deng and Kenneth A. Smith, Dept. of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA

Margaret A. Farrar , Cambridge Rindge and Latin School, Cambridge, MA*DOE GCEP SURE Summer Student, Utah State University*DOE GCEP SURE Summer Student, Cornell University

• AMS collection efficiency:

CE(dva) = EL(dva) × EB(dva) × ES(dva)

Total Lens Bounce Shape

• Want to transmit larger particles (> 1µm) into AMS

• Other applications for AMS, drug delivery particles, bioaerosols.

• PM2.5

Experimental SetupSize Selection

Differential Mobility Analyzer(DMA)

Atomizer

Light Scattering (LS)

Vaporizer

InputCondensation Particle Counter

(CPC)Detection

Aerosol Mass Spectrometer(AMS)

Aerosol Source

Mass Detected = # DetectedMass Input # Input

Detection Ratio =

Standard LensOrifice assembly

Valve body Aerodynamic lens

a)

1.6mm ID

450mm

3.8mm

OD

7”, 178mm

6.055”, 154mm

FEDCBA100 µm orifice Flight

region

b

Lens system

1.2

1.0

0.8

0.6

0.4

0.2

0.0

Tran

smis

sion

Effi

cien

cy (E

L)

102 3 4 5 6 7 8 9

1002 3 4 5 6 7 8 9

10002

Dva (nm)

Experimental Data 585 torr 760 torr

CFD Model 585 torr 760 torr

• Need to model entire lens system, including critical orifice mounting assembly, valve and aerodynamic lens. Loss of particles on steps in plumbing.• Include Brownian motion in lens as well as in flight region.• Still some disagreement between CFD model and experimental measurements.• Transmission Efficiency of an Aerodynamic Focusing Lens System: Comparison of Model Calculations and Laboratory Measurements for the Aerodyne Aerosol Mass Spectrometer , Peter S. K. Liu, Rensheng Deng, Kenneth A. Smith, Leah R. Williams, John T. Jayne, Manjula R. Canagaratna, Kori Moore, Timothy B. Onasch, Douglas R. Worsnop, and Terry Deshler, submitted to AS&T 2006

PM1 DefinitionURG PM1 Cyclone:

http://www.urgcorp.com/cyclones/pdf/2000-30EHB.pdf

• With Jayne et al. transmission, the AMS is approx. a PM1instrument

• dta vs. dva

• With Liu et al. results, less than PM1.

• Note: Jayne et al. results for a different lens (12”, conical nozzle) than current standard lens (7”, flat nozzle).

Jayne et al.2000

PM1 Definition

2 3 4 5 6 7 8 91000

2

Liu et a l.7 60 torr

Reduce Particle Loss Before the LensStandard Lens

Orifice Lens Mass Spec760Torr 2 Torr 0.1Torr

Orifice Lens Mass Spec760Torr 20 Torr 0.1TorrAxial location (m)

Rad

ial l

ocat

ion

(m)

1000nm

Axial location (m)

Rad

ial l

ocat

ion

(m)

1000nm

High Pressure Lens

Converging orifice

High P Lens version 1Scale: Axial(1:1), Radial(1:2)

7”(177.8mm)

34.4mm20mm

19mm

0.2mm

16.5mm4.4mm 2.0mm 1.8mm 1.6mm 1.4mm 1.2mm 1.0mm 0.9mm

1.6mm

2mm

0.8mm

• Based on design published by Schreiner, et al. (1999) Aerosol Sci. Tech. 31: 373-382.• Optimized for constraints of AMS, e.g., lens length, pumping capacity, etc., with CFD calculations (FLUENT)• Small aperture sizes makes machining difficult. First attempts with traditional machining were abysmal failure. • Electrical discharge machining (EDM) worked well.

Orifice-lens assembly

-0.36 -0.30 -0.24 -0.18 -0.12 -0.06 0.00-0.015

-0.010

-0.005

0.000

0.005

0.010

0.015

Nozzle

Diameter of pinhole is 80/100/120 microns.Diameters of connection and lens tube are 4.4mm.Diameter of the nozzle is 1.0mm.

LensConnectionPinhole

Y (m

)

X (m)

Constant bore of 4.4 mm from orifice to lens entrance.“New Inlet”

Results for HP Lens v1

350

300

250

200

150

100

50

0

Parti

cle

Velo

city

(m/s

)

2 3 4 5 6 7 8 9100

2 3 4 5 6 7 8 91000

2 3 4

Daero (nm)

High P Lens, ARI2100 micron orifice

ari2_2_AN_vel ari2_2_AN_LS_vel ari2_2_PSL_vel ari2_2_Na_vel ari2_2_Na_LS_vel ari2_2_Pb_vel ari2_2_Pb_LS_vel

fit_ari2_2_all_velV_param_0 = 408.46 ± 13V_param_1 = 79.599 ± 2.06V_param_2 = 138.57 ± 10.2V_param_3 = 0.97034 ± 0.0369

HP_F_Vel, Deng's calc. vel

1.0

0.8

0.6

0.4

0.2

0.0

Tran

smis

sion

Effi

cien

cy

5 6 7 8 9100

2 3 4 5 6 7 8 91000

2 3 4

Daero (nm)

TE_results_AN_100 TE_results_Na_100 TE_results_Pb_100 Calc_TE_100

1.0 1.0

0.8 0.8

0.6 0.6

0.4 0.4

0.2 0.2

0.0 0.0

Tran

smis

sion

Effi

cien

cy

5 6 7 8 9100

2 3 4 5 6 7 8 91000

2 3 4 5 6

Daero (nm)

ARI2, HighPLens120 micron pinhole

TE_AN_3 TE_AN_LS_3 TE_Na_3 TE_Na_LS_3 TE_Pb_3 TE_Pb_LS_3 wave1, Deng calc.

10 100 1000 10000

0.0

0.2

0.4

0.6

0.8

1.0

10 100 1000 10000

Pinhole(um) 160 140 120 100 80 60

Tr

ansm

issi

on e

ffici

ency

Dp, nm

CFD results for different orifice diameters.

Good agreement between calculated and measured particle velocities.

Experimental results for 100 µm orifice.

Experimental results for 120 µm orifice. Undesirable!

High Pressure Lens v2

Scale: Axial(1:1), Radial(1:2)

7”(177.8mm)

34.4mm20mm

19mm

0.2mm

16.5mm4.95mm 2.25mm 2.024mm1.8mm 1.574mm1.35mm 1.124mm 1.012mm

1.8mm

2mm

0.9mm

All radial dimensions are scaled up from the previous lens by 12.5%, with all axial dimensions fixed.

• Larger apertures gives lower pressure at lens entrance and should shift transmission window to smaller sizes.• We did not scale up the bore of the orifice-valve assembly to 4.95 mm.

Calculated axis pressure

-0.35 -0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00 0.050

150

300

450

600

750

900

Pres

sure

(Tor

r)

Axial location (m)

-0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00 0.050

5

10

15

20

25

30

P=9.1Torr

P=19.0Torr

P=13.6Torr

120um 100um 80um

Pre

ssur

e (T

orr)

Axial location (m)

Calculated transmission efficiency

10 100 1000 100000.0

0.2

0.4

0.6

0.8

1.010 100 1000 10000

o80 o100 o120

Tran

smis

sion

Effi

cien

cy

dp (nm)

O120, Q=108.0sccm(or 118.8ccm at 300K)

Window: 0.115-4.35µm

O100, Q=74.1sccm(or 81.4ccm at 300K)

Window: 0.075-3.5µm

O80, Q=46.9sccm (or 51.5ccm at 300K)

Window: 0.047-1.85µm

Calculated and Measured Particle Velocity

300

250

200

150

100

50

0

Vel

ocity

(m/s

)

2 3 4 5 6 7 8 9100

2 3 4 5 6 7 8 91000

2 3

Dva (nm)

100um pinhole 120um pinhole fit_velocity_100 fit_velocity_120 V_calc_100 V_calc_120

High Pressure Lens: 100 µm Orifice

1.0

0.8

0.6

0.4

0.2

0.0

Det

ectio

n R

atio

2 3 4 5 6 7 8 9

1022 3 4 5 6 7 8 9

1032 3 4 5 6 7 8 9

104

Dva (nm)

High Pressure Lens100µm Orifice

MS NH4NO3 LScnts NH4NO3 LScnts NaNO3 Numerical Calculation

Standard Lens Standard Lens

•Much better transmission efficiency for larger particles (350nm-2µm)•Still not as good as calculated values

High Pressure Lens: 120 µm Orifice1.0

0.8

0.6

0.4

0.2

0.0

Det

ectio

n R

atio

2 3 4 5 6 7 8 9

1022 3 4 5 6 7 8 9

1032 3 4 5 6 7 8 9

104

Dva (nm)

High Pressure Lens120µm Orifice

MS NH4NO3 LScnts NH4NO3 LScnts NaNO3 Numerical Calculation

Standard Lens Standard Lens

• Narrower transmission efficiency than calculation predicts• Slightly better transmission for large particles than standard lens

High Pressure Lens: 70/80 µm Orifice1.0

0.8

0.6

0.4

0.2

0.0

Det

ectio

n R

atio

2 3 4 5 6 7 8 9

1022 3 4 5 6 7 8 9

1032 3 4 5 6 7 8 9

104

Dva (nm)

High Pressure Lens70 µm Orif ice

MScnts NH4NO3 LScnts NH4NO3 LScnts NaNO3 CFD Calculation, 80 µm Standard Lens

• Narrower transmission efficiency than calculation predicts

Calculated particle trajectories

2 µm2µm Particles (scale Y:X =10:1)

1 µm

1µm Particles (scale Y:X =10:1)

0.5µm Particles (scale Y:X =10:1)

0.5 µm

See deposition of material on back of critical orifice. Particles caught in eddies impacting?

Lead Nitrate Data1.2

1.0

0.8

0.6

0.4

0.2

0.0

Det

ectio

n R

atio

2 3 4 5 6 7 8 9

1022 3 4 5 6 7 8 9

1032 3 4 5 6 7 8 9

104

Dva (nm)

High Pressure Lens, New Inlet100 µm Orifice #1

MScnts NH4NO3 LScnts NH4NO3 LScnts NaNO3 LScnts Pb(NO3)2

100 µm Orifice #2 MScnts NH4NO3 LScnts NH4NO3 LScnts NanO3 LScnts Pb(NO3)2

CFD Calculation High P Lens v2 Standard Lens

• Pb(NO3)2 LS cnts (blue circles) indicate significant transmission between 2 and 5 µm.• Detected 1, 3 and 5 µm PSLs in AMS with LS, but not quantified.

5 µm PSL

High Pressure Lens: New Inlet vs Standard Inlet

• New inlet better then standard inlet for large particle sizes.• Standard valve on high pressure lens looks very similar to standard

valve on standard lens.• Confirms calculation result that particles lost in orifice/valve plumbing.

1.0

0.8

0.6

0.4

0.2

0.0

Det

ectio

n R

atio

2 3 4 5 6 7 8 9

1022 3 4 5 6 7 8 9

1032 3 4 5 6 7 8 9

104

Dva (nm)

High Pressure Lens100µm orificeConstant Bore Valve

MS NH4NO3 LScnts NH4NO3

LScnts NaNO3 Numerical Calculation

Standard Valve MScnts NH4NO3 LScnts NH4NO3 Standard Lens

Standard Lens: New Inlet vs Standard Inlet

1.0

0.8

0.6

0.4

0.2

0.0

Det

ectio

n R

atio

4 5 6 7 8 9100

2 3 4 5 6 7 8 91000

Dva (nm)

Standard Lens100µm OrificeConstant Bore Valve

MS NH4NO3 LScnts NH4NO3 LScnts NaNO3

Standard Valve MS NH4NO3 LScnts NH4NO3 LScnts NaNO3 Standard Lens

•Inlet does not have a large effect on standard lens system.

Pressure Controlled Inlet• 0.25 mm aperture, tee to pump, 150 µm orifice, tee to pressure gauge.

• Vary pressure at lens entrance from 12 torr to 23 torr.

Pump

0.25 mm 150 µm

100 torrBaratron

Valve HPL v2

Needle Valve

Pressure Controlled Inlet Results1.2

1.0

0.8

0.6

0.4

0.2

0.0

TE

4 5 6 7 8 9100

2 3 4 5 6 7 8 91000

2 3 4 5 6

Dmob (nm)

PInlet_12 torr Pinlet_14 torr PInlet_16 torr PInlet_19 torr Pinlet_23 torr

• Lower pressure shifts transmission window to smaller particle sizes.• Above 20 torr, problems with transmission at all sizes. Related to eddies?

1.2

1.0

0.8

0.6

0.4

0.2

0.0

TE

4 5 6 7 8 9100

2 3 4 5 6 7 8 91000

2 3 4 5 6

Dmob (nm)

Pinlet_14 torr TE_100 HPL v2

1.2

1.0

0.8

0.6

0.4

0.2

0.0

TE4 5 6 7 8 9

1002 3 4 5 6 7 8 9

10002 3 4 5 6

Dmob (nm)

PInlet_19 torr TE_120 HPL v2

Pressure Controlled Inlet Results

• Comparison of pressure controlled inlet with HPL v2 at same pressures as 100 µm orifice and 120 µm orifice. • At 14 torr, extra plumbing removes larger particles. At 19 torr, extra plumbing doesn’t make much difference.

Conclusions

• Better transmission of 600 nm to 2 µm particles, but still a work in progress.

• Smooth bore inlet helps with high P lens, but not with standard lens.

• Some things not captured by calculations, e.g., deposition on back of orifice.