1. TSI Incorporated Seeding of Flows TSI LDV/PDPA Workshop & Training Presented by Joseph Shakal Ph.D.

2. TSI Incorporated Copyright 2008 TSI Incorporated Seeding Most neglected aspect in LDV Proper seeding can significantly increase measurement accuracy and rate Key parameter to optimize SNR Guidelines for selection Related issues TSI Particle Generators

3. TSI Incorporated Copyright 2008 TSI Incorporated Solid Seed Particles 25um & 40um Glass Beads PSL TiO2 10-40um Silver Coated HGB 4um Nylon

4. TSI Incorporated Copyright 2008 TSI Incorporated Requirements Single Particle Parameters –Aerodynamic size –Signal strength (surface properties) –Safety and Compatibility with Test Equipment Composite Parameters –Concentration –Monodispersity –Size of Flow System TSI 3400A Fluidized Bed Particle Generator

5. TSI Incorporated Copyright 2008 TSI Incorporated Requirements Safety Parameters –Use Olive Oil – Toxicity: see MSDS –Flammability –System Compatibility: will moving parts be damaged by the particles? TSI 9307 Particle Generator

6. TSI Incorporated Copyright 2008 TSI Incorporated Particle Size Distributions 051015 Diameter 20 Volume (Mass) Based VMD = 5  m Number Based NMD =.4  m Diameter 0.1110100 Diameter 0204060 Diameter (Linear) (Log)

7. TSI Incorporated Copyright 2008 TSI Incorporated Seeding Techniques for Air Flows Generate liquid droplets –Direct use of generated droplets –Start with solution- leaves solid particle of solute when dry –Start with mixture of high & low vapor pressure materials (e.g., oil and alcohol) –Disperse solid particles suspended in a liquid by drying droplets Disperse dry powders Evaporation and condensation of a liquid –(Evaporation condensation generator) –TSI 9308 ‘Fog Generator’

8. TSI Incorporated Copyright 2008 TSI Incorporated Seed Particle Requirements Water and Air Water (n = 1.33) –Forward-scatter Generally no seeding is required –Backscatter Seeding often necessary Air (n = 1.0) –Seeding usually desirable

9. TSI Incorporated Copyright 2008 TSI Incorporated Seeding Water for Backscatter Conditions Laser - Argon-ionBeam spacing - 35 mm Power - 0.7 WBeam expansion - 3.75x F.L. - 450 mmMaximum velocity - 10 m/s Aperture - 150 mmSpherical particles SNR (dB) Settling Velocity (µm/s) ParticleTiO 2 PSLTiO 2 PSL Diameter(n = 2.9)(n = 1.59)(s.g. = 4.26)(s.g. = 1.05) 0.25 35.80.10 0.5449.821.80.470.008 1.0029.30.027

10. TSI Incorporated Copyright 2008 TSI Incorporated Particle Motion Relative to Fluid Ref: Feller & Myers (1976 ) Note that these relations could easily be made into a spreadsheet for to help with seeding particle selection.

11. TSI Incorporated Copyright 2008 TSI Incorporated Particle Response in Air 0.5 µm 1 µm 2 µm f 3db f 3db f 3db Particles in Airn  t 1 (µs)(kHz)t 1 (µs)(kHz)t 1 (µs)(kHz) Silicon Carbide2.6 3.3 2.556310.2 1641 3.9 Alumina1.763.8 2.935411.7 1447 3.0 Polystyrene1.6 1.050.81196 3.245213 13 Peanut Oil1.470.910.70227 2.815711.2 14 Microballoons—0.230.18897 0.71224 2.8456 For air, settling velocity = 9.8 x Time Constant (t 1 ) in m/s Time Constant and Frequency Response

12. TSI Incorporated Copyright 2008 TSI Incorporated Particle Response in Water Settling Velocity (µm/s) Particles m 0.5 µm1 µm2 µm5 µm Silicon Carbide1.950.31 1.2 5.0 30 Alumina1.320.38 1.4 6.0 38 Polystyrene1.2 0.0070.0270.110.68 Relative refractive index m = n p /n w

13. TSI Incorporated Copyright 2008 TSI Incorporated Seed Particles - Air and Water Particles MediumDensityRefractiveDia (g/cc) Index (  m) Silicon Carbide Air/Water 3.22.651.5 Nylon Air/Water 1.141.534.0 PSLAir 1.051.55-1.60.5 TiO 2 Air/Water 4.22.63-5 Hollow Glass Beads (HGB)Air 1.05 - 1.15?1.58-12 Silver Coated HGBWater 1.650.21 (R)14 2.62 (I) Olive OilAir 0.921.47---

14. TSI Incorporated Copyright 2008 TSI Incorporated Other Comments Anti-static additives can help prevent particles from sticking to glass or acrylic windows. Larostat is commercially available. Hydrophobic (Anti-fogging) coatings are now available for windows. Abrisa Corp can supply this type of window, also with AR coating. ‘Transparent’ conductive film is available to prevent static buildup on windows, & thus prevent particles from sticking. Initial results appear promising. Customer at Brigham-Young Univ. has done testing.

15. TSI Incorporated Copyright 2008 TSI Incorporated Summary Careful selection of particles can offer much improved signals in backscatter measurements in water In air, TSI atomizers are a proven liquid particle generation technique Solid Particles: –No universal solution –Acceptable particles and dispersion technique normally available for a given application.