United States
Environmental Protection
Agency
Environmental Sciences Research*^
Laboratory •
Research Triangle Park NC 27711
Research and Development
EPA-600/S3-82-039 May 1982
Project Summary
Design, Fabrication and
Testing of Ambient Aerosol
Sampler Inlets
^ James B. Wedding and Michael A. Weigand
s?
-------
mVmin (50 cfm). The collection effec-
tiveness of this sampler, however, was
found strongly dependent on particle
size, approach flow wind speed, and
sampler orientation.
Growing recognition of the defici-
encies in both the TSP standard and the
Hi-Vol sampler by which the standard
has been implemented has led the U.S.
Environmental Protection Agency (EPA)
to consider a new category of ambient
aerosol referred to as Inhalable Particu-
late Matter (IPM). Currently, IPM is
defined as those particles having aero-
dynamic diameters < 15//m. Ideally the
inlet of an IPM sampler would transmit
100% of all particles smaller than 15
urn, independent of the ambient wind
speed which carried the particles toward
the inlet, and would not transmit the
larger particles. An infinitely sharp
cutpoint and strict independence of wind
speed cannot be achieved in practice,
however. Instead, the 15 urn cutpoint is
taken to be the particle size at which the
collection effectiveness is 50%, and the
collection effectiveness for all particle
sizes must fall within a prescribed IPM
performance envelope over a specified
range of wind speeds (2 to 24 km/h).
The project report describes an inlet
developed at Colorado State University
intended for IPM sampling, and provides
data from the wind tunnel testing of the
resulting inlet. Additionally, measure-
ments are reported on the wind tunnel
testing of a second candidate IPM inlet
developed in a joint effort between the
University of Minnesota (UM) and
Lawrence Berkeley Laboratory (LBL).
Both inlets operate at a flow rate of 16.7
L/min and thus are suitable as replace-
ment inlets for existing dichotomous
samplers.
Inlet Descriptions
Figure 1 shows the inlet developed at
the Aerosol Science Laboratory, Colo-
rado State University (ASL/Wedding
inlet). The housing for the inlet is similar
to that of the current commercial inlet
for the dichotomous sampler. The par-
ticle size fractionator component of the
cyclone receives an angular impetus as
it follows a channel defined by two
adjacent curved directional vanes, and
accelerates toward the outer radius of
the cyclone R2. When the particle arrives
at R2 with velocity Uo, it begins its
upward ascension with velocity Uv. If
the particle is not removed, it will travel
the distance I, negotiate the turn at the
top of the cyclone Ri and travel down-
ward to the exit plane of the inlet.
Particles that are removed are intended
to deposit on the inside collector surface,
as shown in Figure 1.
Figure 2 shows the inlet developed
jointly by UM and LBL The fractionator
component of the inlet is an impaction
stem and cup.
Results
The two inlets were tested in the
closed-loop ASL Wind Tunnel. The
tunnel has a cross-sectional dimension
of 1.22 m square at the test section.
Monodisperse aerosol supplied to the
tunnel is generated by a vibrating orifice
atomizer operated in an inverted man-
ner. Particles employed in the study
Collecting
surface
8
Directional
Vanes
2cm
Inlet
housing
Entrance
plane
Figure 1. Wedding IPM inlet.
-------
were made from an oleic acid-ethanol
mixture tagged with uranine.
Results from the wind tunnel tests on
the sampling effectiveness of the Wed-
ding inlet are shown in Figure 3. Each
plotted point represents the average
value of at least eight data points taken
on different days. Tests are quickly and
reproducibly performed for speeds of 2
to 24 km/h (and greater). For the 0.5
and 2. km/h tests, fluid energy is insuf-
ficient to mix adequately the injected
aerosol—thus the greater error potential
must be noted. Except for an enrichment
condition below 10 fjm at 24 km/h the
measurements shown in Figure 3 for
the Wedding inlet fall within the IPM
performance envelope. The DM values
at 0.5, 2, 8, and 24 km/h are 14.4,14.0,
14.2, and 13.7>um, respectively. (D5o is
Circular
cover
Spacer (3)
Support
post
Impact/on
cup
Deflection
cone
Impact/on
nozzle
Impact/on
head
Inertia!
trap
Reducer for
connection
to sampler
AH dimensions in centimeters
Figure 2. UMLBL IPM inlet.
the particle diameter for which the
sampling effectiveness is 50%.)
The UMLBL inlet results are given in
Figure 4. Within experimental error the
measurements fall within the IPM per-
formance envelope, except for the 5pm
points at 2 and 24 km/h. Independent
measurements performed at UM
showed a virtually identical enrichment
at 24 km/h, but all measurements at 1
km/h were within the limits of the IPM
performance envelope. The differences
between the two sets of measurements,
although small, are unresolved at pres-
ent.
Conclusions and
Recommendations
A candidate IPM inlet was designed,
fabricated, and tested in a wind tunnel.
On the basis of the tests it is recom-
mended as a reasonable interim choice
for use on EPA's IPM dichotomous
sampler network. A new completely
revised fractionator and inlet housing
concept are presently being designed
and tested specifically to eliminate an
enrichment condition exhibited by the
inlet, to make the unit more compact
and versatile, and to improve perform-
ance characteristics of the cyclone
fractionator. The fractionator should
cause the mass to deposit in more
favorable locations. The redesign was
initiated in July 1980 under a different
project and is currently underway.
Wind tunnel testing was performed
on a second inlet provided by the UM
and LBL. While the tests showed UMLBL
inlet to be in near compliance with the
presently proposed IPM performance
envelope, independent measurements
at the UM have shown a slightly better
performance. The differences between
the two sets of measurements, although
small, remain unresolved and may
indicate the degree of uncertainty in
such measurements at the present time.
The technology represented by each
of these inlets does not purport to be the
ultimate answer to IPM sampling needs.
As health effects and other environ-
mental factors and national/scientific
needs dictate monitoring strategy
changes (e.g., D5o, flow rates), other
inlet systems will need to be developed.
As this report was being completed, a
change in Dsofor IPM from 15to 10/um
is under serious consideration. Although
the inlets discussed in this report would
then no longer be appropriate, the
principles of their design are adaptable
to a new cutpoint choice.
-------
120
110\-
100
IPM Performance
envelope
6.7% !y 0.5
6.6% \ o 2.
[2.6%j Q 8.
2.4% j A 24.
14.4 1.340 1.272
14.0 1.191 7.200
14.2 1.092 1.186
13.7 1.096 1.166
3 4 5 6 7 8 9 10
Aerodynamic diameter, fim
Figure 3. Sampling effectiveness for Wedding inlet.
40 50
-------
110
100
90
80
* 70
I
« 60
I.
40
30
20
10
IPM Performance
envelope
u of m
Inlet
±6.6%
±2.6%
±2.4%
t/oo
km/hr
• 2
D 8
A 24
y
A
I
4 5 6 7 8 910
Aerodynamic diameter,
20
30 40 SO
Figure 4. Sampling effectiveness for UMLBL inlet.
-------
James B. Wedding and Michael A. Weigand are with the Research Institute of
Colorado, Fort Collins. CO 80526.
Charles W. Lewis is the EPA Project Officer (see below).
The complete report, entitled "Design, Fabrication and Testing of Ambient
Aerosol Sampler Inlets," (Order No. PB 82-198 417; Cost: $7.50, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
OUSGPO: 1982 — 559-092/3403
-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Postage and
Fees Paid
Environmental
Protection
Agency
EPA 335
Official Business
Penalty for Private Use $300
"» Xk-uTR PRUt tv- ' iu
SSSssa-1
AGENCY
------- |