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?  


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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.

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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.

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  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

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   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.

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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

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