Characterization Methods for Spray Drying Nozzles
An Overview
En’Urga Inc.
1201 Cumberland Avenue, West Lafayette, IN 47906
http://www.enurga.com
Motivation
Spray drying used for producing
powder from a liquid or slurry
Food, pharmaceuticals, consumer
products
Can convert APIs from crystalline
to amorphous form for improved
bio-availability
All spray dryers use some type of
nozzles
Quality of nozzle determines the
final product quality
Outline
Spray Characterization Methods
Sample Results
Spray characterization work at En’Urga Inc.
Spray Characterization Methods
Spray Characterization Methods
Phase Doppler interferometry
Fraunhofer diffraction
Laser sheet imaging
Extinction tomography
Imaging velocimetry
Holographic imaging
Laser induced Fluorescence
X-Ray visualization
Phase Doppler Interferometry
Fringe pattern from
2 laser beams
Particle scatters light
and projects pattern
Detector at one
angle provides
velocity
Multiple detectors
provide size
Multiple setting
required for wide
dynamic range
Measurement Characteristics
Aerosol limitations Spherical, transparent/opaque
Distance to sample < 3m
Probe volume small
Size 1-500m
Number limitation Coincident, extinction
Sampling type Flux dependent
Measured quantities Velocity, size
Dynamic range 50
Sampling mode Time averaged, time resolved
Sensitivity highest large drops
Fraunhofer Diffraction
Scattered intensity
from laser beam
Fourier transform lens
for discrimination
Array detectors
measures intensity at
different angles
Mie scattering theory
for particle size
Beam wandering a
problem in
evaporating fluids
Measurement Characteristics
Aerosol limitations None on shape/better if opaque
Distance to sample < 0.5 m
Probe volume Line of sight
Size 0.3-500 m
Number limitation Extinction, multiple scattering
Sampling type Concentration
Measured quantities Size
Dynamic range 100
Sampling mode Time averaged, time resolved
Sensitivity highest Middle range of drop sizes
Laser Sheet Imaging
Laser sheet to illuminate spray
Image taken using a CCD camera
at an oblique angle
Intensity proportional to drop
surface area per unit volume
Potential Errors
Laser extinction
Signal attenuation
Secondary emission
Measurement Characteristics
Aerosol limitations Spherical particles
Distance to sample < 0.5 m
Probe volume Planar, volume
Size 3-unlimited
Number limitation Extinction, image overlap
Sampling type Concentration dependent
Measured quantities Light intensity
Dynamic range 20
Sampling mode Instantaneous
Sensitivity highest Largest drops
Extinction Tomography (SETscan)
Spray
Array
detector
Laser
Laser sheet
Principle of Operation
Path integrated extinction of laser sheets
Multiple view angles for non-axisymmetric
turbulent flows
Multiple slices to obtain high spatial resolution
Local extinction coefficients obtained by statistical
tomography (MLE method)
For liquid sprays, the local extinction coefficients is
equal to the drop surface areas per unit volume
Measurement Characteristics
Aerosol limitations Unrestricted
Distance to sample Unrestricted
Probe volume Planar
Size Unrestricted
Number limitation Extinction
Sampling type Concentration
Measured quantities Surface area * no. of drops/m3
Dynamic range Instrument SNR
Sampling mode Instantaneous, time averaged,
time resolved
Sensitivity highest Uniform across range
Imaging Velocimetry
Two types available
Planar Particle Imaging
Velocimetry and Statistical
Pattern Imaging Velocimetry
First type tracks individual
particles and determines
displacement
Second type tracks flow patterns
and determines peak spatial
correlations over a fixed time
window
Advantages and Disadvantages of SPIV
Advantages
Does not require distinct particles
Works with various types of lighting such as
shadowgraphy and natural lighting
Work equally well with dense sprays
High powered lasers not required
Disadvantages
Bimodal velocity difficult to resolve
Longer computational time required
Minimum 10 KHz camera
Holographic Imaging
M – Mirror
L – Lens
BS – Beam splitter
Scattered or shadow images mixed with a
reference beam
Interference pattern on holographic film
Image reconstructed to obtain particle size/shape
Planar Laser Induced Fluorescence
Fuel, sometimes mixed with Dopant
Excited with laser sheet
Fluorescence observed with CCD array
Intensity proportional to volume fraction
Potential Errors
Spray
Beam
expander Laser extinction
Nd: YAG
laser
Signal attenuation
Beam stop Shot-to-shot variation
Cylindrical
lens Laser sheet
CCD
Camera
X-Ray visualization
X-Ray
source
X-Ray detector
array
Injector
Ideal for dense sprays (light cannot penetrate)
Used to obtain planar mass concentration
Works with particles, gases, and liquids
Comparison of Methods
Measurement Characteristics Light Scattering Fraunhofer Light Sheet Imaging Extinction
Interferometry Diffraction, Ensem Tomography
Basic Measurement Diameter/Velocity Diameter Pattern Surface area
Accuracy +/- 20% +/- 20% Not quantitative +/- 2%
Particle Shape Restriction Spherical Sphere,Irregular Spherical none
Particle Composition Transparent, Opaque Better if opaque None none
Index of Refraction Dependence Yes Partial/none None None/Imaginary
Working distance (Trans to Det) 3 m 0.5 m 0.5m Unlimited
Sample Volume Small, Point Line of site Plane/volume Plane/volume
Sample Volume Bias Yes, Correction None Yes, Correction None
Size Minimum, mm 0.3 0.3 3 Unlimited
Maximum size 1,000 500 unlimited Unlimited
Number Density Maximum Coincid/extinction Extinction/MultiScat Extinction/overlap Extinction
Number Density Minimum None Yes, Low SNR Blank Images Low SNR
Sampling Type Flux Dependent Concentration Concentration N/A
Sampling Mode Time ave/ Instantaneous/ Instantaneous Time Ave, Time
Time Resolved Time Reolved Resolved, Instant
Size Dynamic Range 50 50 20 N/A
Particle Velocity Yes No Possible Possible
Number Density Measurements Yes Yes, With extinction Yes Yes
Measurement Sensitivity Highest for largest Highest for middle Highest for largest Uniform across range
Why surface area density
Total amount of fuel or liquid evaporated is
proportional to heat release rate in combustion
and solid mass fraction in spray drying.
Correlation coefficient (R) of different
parameters with total fuel evaporated
Mass flux R = 0.903 Velocity R = -0.239
Diameter = 0.681 Surface area density = 0.961
For combustion and spray drying applications, surface
area density is optimal method of comparing different
nozzles or checking uniformity
Sample Results
Sample Results (PDA)
16
40psi, 40gpm
14 40psi, 150gpm
70psi, 40gpm
70psi, 150gpm
V
12
70psi, 400gpm
100psi, 150gpm
Y-Velocity (m/s)
10 100psi, 400gpm
y 8
0
-50 -40 -30 -20 -10 0 10 20 30 40 50
Radial Position (mm)
Diameter vs. Radial Position (90 sweep)
6
100
70psi, 40gpm
70psi, 150gpm 90
4 70psi, 400gpm
80
70
2
X-Velocity (m/s)
Diameter (microns)
60
0 50
40
-2
30
20 100psi, 4.75% D.C
-4
100psi, 23% D.C
10
100psi, 73% D.C
0
-6
-50 -40 -30 -20 -10 0 10 20 30 40 50
-50 -40 -30 -20 -10 0 10 20 30 40 50
Radial Position (mm)
Radial Position (mm)
Sample Results (Malvern)
40 PSI, Malvern Data Test 4 40 g/min, D32
300 40 g/min, D43
40 g/min, D90
250 40 g/min, D10
Characteristic diameters, m
40 g/min, D50
40 g/min, D30
200 150 g/min, D32
150 g/min, D43
150 150 g/min, D90
150 g/min, D10
150 g/min, D50
100 150 g/min, D30
333 g/min, D32
50 333 g/min, D43 Single line data
333 g/min, D90 Two data
333 g/min, D10
0
333 g/min, D50
points at each
-2.0 -1.0 0.0 1.0 333g/min, D30 condition
Distance, inches
Sample Measurement (effect of vapor)
0 .2 5
D r o p s iz e d is t r ib u t io n n e g le c t in g f ir s t 4 r in g s
D r o p s iz e d is t r ib u t io n n e g le c t in g f ir s t 9 r in g s
0 .2 0
S M D c a s e 1 = 2 9 . 0 5 m ic r o n s
S M D c a s e 2 = 1 2 . 7 3 m ic r o n s
% volume in bin
0 .1 5
0 .1 0
0 .0 5
0 .0 0
0 20 0 400 600 800 1000
D r o p s iz e ( m ic r o n s )
Effect of fuel vapor (beam wandering) is to cause spurious
readings of large drops
Recommendation is to neglect reading of first 9 rings or all drops
larger than 150 microns
Injector manufactures report case 2
Sample Results Patternator
Struts signature
seen in drop
surface area map
Hollow cone seen
as hollow
Drip from nozzle
seen at the center
Sample Result: Agricultural Nozzle
Ensemble average of drop surface area density
High/low surface area indicates streaks/voids
Sample results from X-Ray
Deconvoluted
Deconvoluted results
results of mass
of mass fraction
fraction of water
of water
Lower
With SPIV, flow rate has
provides masshigher local concentration
flux within 5%
High flow
With patternator rate had
provides larger
drop size footprint
within 20%
SPIV shadowgraphy (penetration velocity)
70
Cond1 Injector # 86
Cond2
60
Cond3
Cond4
50 Cond5
Cond6
Distance (mm)
40
30
20
10
0
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Time (ms)
Sample Results SPIV
GDI Injector at 20 MPa
PDA vs Patternator
Patternators Extinction 1/mm
Calculated Absorption Contour Plot 1/mm
0.03
10 10
0.02
0.025
5
5
0.015 0.02
Y (mm)
0
Y (cm)
0
0.01 0.015
-5
-5 0.01
0.005 -10
-10 0.005
-15
-15 -10 -5 0 5 10 15 -15 -10 -5 0 5 10
X (cm) X (mm)
Patternators Extinction 1/mmx 10-3
Calculated Absorption Contour Plot 1/mmx 10-3
7
20 20
5 6
10 10
4 5
Y (mm)
Y (cm)
0 0
3 4
-10
-10 2 3
-20 2
-20 1
-40 -20 0 20 40
-40 -20 0 20 40 X (mm)
X (cm)
Velocimeter vs PDA
Spray characterization at En’Urga Inc.
Current Spray Instruments
Optical patternator Large area patternator
X-Ray mass flow meter Pattern Imaging Velocimeter
Instruments under development
Planar drop sizer
SMD P= 50 PSI
20
10
Distance (mm)
0
-10
-20
-20 -10 0 10 20
Distance (mm)
Fluorescence tomography
120
Fluorescence Tomography
100 PDA measurement
P = 100 psi, X= 30 mm
80
Drop Size (m)
60
40
20
0
-20 -15 -10 -5 0 5 10 15 20
Radial Distance (mm)
