1
MEMORANDUM
DATE:
January
8,
2004
SUBJECT:
Engine
Operation
at
Colorado
State
University
(
CSU)

FROM:
Tanya
Ali
Alpha­
Gamma
Technologies,
Inc.

TO:
Sims
Roy,
EPA
OAQPS
ESD
Combustion
Group
The
purpose
of
this
memorandum
is
to
demonstrate
that
the
2
stroke
lean
burn
(
2SLB)
engine
and
4
stroke
lean
burn
(
4SLB)
engine
operating
conditions
during
EPA's
testing
at
Colorado
State
University
(
CSU)
are
representative
of
2SLB
and
4SLB
engine
operating
conditions
in
the
field.

Background
On
December
19,
2002,
EPA
proposed
national
emission
standards
for
hazardous
air
pollutants
(
NESHAP)
for
stationary
reciprocating
internal
combustion
engines
(
RICE)
(
67
FR
77830).
During
the
public
comment
period,
EPA
received
comments
stating
that
the
data
from
the
testing
of
the
2SLB
and
4SLB
engines
at
CSU
should
be
disallowed.
Comments
received
indicated
that
certain
parameters
such
as
the
oxygen
levels,
exhaust
temperatures,
and
nitrogen
oxides
(
NOx)
levels
are
not
typical
and
that
the
2SLB
and
4SLB
engines
tested
at
CSU
are
not
representative
of
engines
in
industry.
A
more
complete
summary
of
the
comments
EPA
received
on
this
issue
can
be
found
in
the
memorandum
entitled
"
Response
to
Public
Comments
on
Proposed
Stationary
Reciprocating
Internal
Combustion
Engines
NESHAP,"
available
from
EPA's
docket
(
Docket
ID
Nos.
OAR­
2002­
0059
or
A­
95­
35).
In
order
to
develop
a
response
to
these
comments,
EPA
reviewed
the
Emissions
Database
to
compare
the
oxygen
levels,
exhaust
temperatures,
and
NOx
levels
from
the
2SLB
and
4SLB
engines
tested
at
CSU
to
other
2SLB
and
4SLB
test
results
in
the
Emissions
Database.

Review
of
Emissions
Database
In
order
to
respond
to
comments
that
certain
engine
operating
parameters
for
the
2SLB
and
4SLB
engines
tested
at
CSU
were
not
typical
of
engines
operating
in
the
field,
EPA
reviewed
the
Emissions
Database
and
compared
the
oxygen
levels,
exhaust
2
temperatures,
and
NOx
levels
observed
at
CSU
to
these
parameters
for
other
engines,
tested
elsewhere.
The
results
of
this
review
and
comparison
are
described
in
the
following
sections.

Oxygen
Levels
The
EPA
received
comments
that
the
range
of
oxygen
levels
observed
at
CSU
were
not
typical
of
2SLB
and
4SLB
engines.
The
EPA
examined
the
Emissions
Database
which
contains
oxygen
levels
for
engines
tested
at
other
locations
besides
CSU.

For
2SLB
engines,
the
average
oxygen
level
for
non­
CSU
tests
was
14.4
percent.
The
minimum
and
maximum
oxygen
levels
for
non­
CSU
tests
were
7
and
19
percent,
respectively.
The
average
oxygen
level
for
the
2SLB
engine
tested
at
CSU
was
15
percent.
The
minimum
and
maximum
oxygen
levels
for
the
2SLB
engine
tested
at
CSU
were
about
14
and
16
percent,
respectively.
As
these
numbers
indicate,
the
oxygen
levels
observed
at
CSU
for
the
2SLB
engine
are
not
beyond
the
range
of
oxygen
levels
observed
for
other
2SLB
engines.
The
EPA,
therefore,
disagrees
with
the
commenter
that
the
oxygen
levels
observed
at
CSU
at
not
typical
of
other
2SLB
engines.

For
4SLB
engines,
the
EPA
also
disagrees
with
the
commenter.
The
average
oxygen
level
for
the
4SLB
engines
in
the
Emissions
Database
that
were
not
tested
at
CSU
was
10.2
percent.
The
minimum
and
maximum
oxygen
levels
for
these
engines
were
4.5
and
17
percent,
respectively.
The
average
oxygen
level
for
the
4SLB
engine
tested
at
CSU
was
9.9
percent.
The
minimum
and
maximum
oxygen
levels
for
the
4SLB
engine
tested
at
CSU
were
about
9
and
10.5,
respectively.
As
before,
these
numbers
indicate
that
the
oxygen
levels
observed
at
CSU
for
the
4SLB
engine
are
within
the
range
of
oxygen
levels
observed
for
other
4SLB
engines.
The
EPA,
therefore,
believes
that
the
oxygen
levels
for
the
4SLB
engine
tested
at
CSU
are
typical
of
other
4SLB
engines.

Exhaust
Temperatures
The
EPA
also
received
comments
that
the
exhaust
temperatures
for
the
2SLB
and
4SLB
engines
tested
at
CSU
were
not
typical
of
other
2SLB
and
4SLB
engines.
The
EPA
reviewed
the
Emissions
Database
and
compared
exhaust
temperatures
of
other
2SLB
and
4SLB
engines
not
tested
at
CSU
to
the
exhaust
temperatures
observed
at
CSU.

For
2SLB
engines,
the
average
exhaust
temperature
for
engines
not
tested
at
CSU
was
623

F.
The
exhaust
temperatures
for
these
engines
ranged
from
455

F
to
1,092

F.
In
comparison,
for
the
2SLB
engine
tested
at
CSU,
the
average
exhaust
temperature
was
535

F,
with
a
minimum
temperature
of
450

F
and
a
maximum
temperature
of
595

F.
The
exhaust
temperatures
observed
at
CSU
for
the
2SLB
engine
tested
are
not
significantly
different
than
the
exhaust
temperatures
measured
for
2SLB
engines
tested
3
elsewhere.
For
this
reason,
EPA
disagrees
with
the
commenter
that
the
exhaust
temperatures
measured
at
CSU
for
the
2SLB
engine
tested
are
not
typical
of
other
2SLB
engines.

For
4SLB
engines,
the
average
exhaust
temperature
for
engines
not
tested
at
CSU
was
839

F.
The
minimum
and
maximum
exhaust
temperatures
for
these
engines
were
592

F
and
1,190

F,
respectively.
In
comparison,
the
average
exhaust
temperature
for
the
4SLB
engine
tested
at
CSU
was
723

F.
For
this
engine,
the
minimum
and
maximum
exhaust
temperatures
were
663

F
and
767

F,
respectively.
The
range
of
exhaust
temperatures
observed
at
CSU
for
the
4SLB
engine
is
within
the
range
of
exhaust
temperatures
for
other
4SLB
engines.
The
EPA,
therefore,
disagrees
with
the
commenter
that
the
exhaust
temperatures
for
the
4SLB
engines
tested
at
CSU
are
not
typical
of
other
4SLB
engines.

NOx
Levels
Comments
received
stated
that
the
NOx
levels
measured
at
CSU
for
the
2SLB
and
4SLB
engines
tested
were
extremely
low.
One
commenter
stated
that
the
range
of
engine
operating
conditions
in
the
testing
of
the
2SLB
engine
and
quite
probably
the
4SLB
engine
is
far
leaner
than
the
leanest
engine
in
the
pipeline
RICE
fleet.
The
commenter
stated
that
this
is
indicated
by
the
extremely
low
NOx
emissions.
In
response
to
this
comment,
EPA
looked
at
the
NOx
levels
for
the
2SLB
and
4SLB
engines
tested
at
CSU
and
compared
the
NOx
levels
to
the
NOx
levels
of
other
2SLB
and
4SLB
engines
in
the
Emissions
Database.

For
2SLB
engines,
EPA
compared
the
NOx
levels
of
2SLB
engines
with
NOx
control.
The
EPA
could
not
make
a
comparison
of
NOx
levels
for
2SLB
engines
without
NOx
control
since
the
2SLB
engine
at
CSU
was
equipped
with
a
pre­
combustion
chamber
­
a
technology
that
alters
the
combustion
process
to
reduce
NOx.
The
average
NOx
level
for
the
2SLB
engine
tested
at
CSU
was
101
parts
per
million
(
ppm).
The
NOx
levels
for
this
engine
ranged
from
8
to
314
ppm.
In
comparison,
the
average
NOx
level
from
other
2SLB
engines
in
the
Emissions
Database
with
NOx
controls
was
106
ppm.
The
NOx
levels
ranged
from
19
to
288
ppm.
As
the
numbers
show,
the
NOx
levels
at
CSU
were
not
beyond
the
range
of
NOx
levels
observed
for
other
engines
in
the
field
and
the
average
NOx
level
at
CSU
was
very
close
to
the
average
NOx
level
for
other
2SLB
engines.
The
EPA,
therefore,
disagrees
with
the
commenter
and
believes
that
the
NOx
levels
measured
at
CSU
for
the
2SLB
engine
are
not
extremely
low
compared
to
other
2SLB
engines
tested
elsewhere
and
does
not
believe
the
2SLB
engine
tested
at
CSU
is
particularly
leaner
than
other
2SLB
engines
in
the
pipeline
RICE
fleet.

For
4SLB
engines,
EPA
again
compared
the
NOx
levels
of
4SLB
engines
with
NOx
control.
The
average
NOx
level
for
the
4SLB
engine
tested
at
CSU
was
62
ppm.
The
range
of
NOx
levels
observed
at
CSU
for
the
4SLB
engine
was
37
to
106
ppm.
In
4
comparison,
the
average
NOx
level
from
other
4SLB
engines
in
the
Emissions
Database
was
83
ppm.
The
NOx
levels
ranged
from
31
to
372
ppm.
The
NOx
levels
observed
at
CSU
for
the
4SLB
engine
tested
are
not
beyond
the
range
of
NOx
levels
measured
at
other
facilities
with
4SLB
engines.
In
fact,
the
numbers
show
that
the
NOx
levels
seen
at
CSU
for
the
4SLB
engine
are
within
the
range
of
NOx
levels
for
other
engines
operating
in
the
field.
The
EPA,
therefore,
disagrees
with
the
commenter
and
believes
the
test
results
from
the
4SLB
engine
tested
at
CSU
are
representative
and
the
NOx
levels
do
not
indicate
that
the
engine
was
significantly
leaner
than
other
4SLB
engines
in
the
field.

Conclusion
Based
on
the
analysis
EPA
performed,
which
consisted
of
analyzing
the
Emissions
Database
to
compare
engine
operating
parameters
of
the
2SLB
and
4SLB
engines
tested
at
CSU
and
the
engine
operating
parameters
of
other
2SLB
and
4SLB
engines
that
are
in
the
Emissions
Database,
EPA
believes
the
engine
operating
parameters
at
CSU
were
appropriate.
The
analysis
presented
in
this
memorandum
shows
that
the
oxygen
levels,
exhaust
temperatures,
and
NOx
levels
measured
at
CSU
for
the
2SLB
and
4SLB
engines
tested
are
within
the
levels
measured
for
other
2SLB
and
4SLB
engines
tested
elsewhere.
The
test
results
obtained
at
CSU
for
the
2SLB
and
4SLB
engine
are
therefore
representative
and
should
not
be
excluded
EPA's
emission
standards
analysis.
