U.S. patent application number 11/496376 was filed with the patent office on 2007-10-04 for exhaust purification with on-board ammonia production.
Invention is credited to James Joshua Driscoll, William L. JR. Easley, Wade J. Robel, Stephan D. Roozenboom.
Application Number | 20070227143 11/496376 |
Document ID | / |
Family ID | 38556856 |
Filed Date | 2007-10-04 |
United States Patent
Application |
20070227143 |
Kind Code |
A1 |
Robel; Wade J. ; et
al. |
October 4, 2007 |
Exhaust purification with on-board ammonia production
Abstract
A first aspect of the present disclosure includes a power source
for use with selective catalytic reduction systems for exhaust-gas
purification. The power source may comprise a first cylinder group
with a first air-intake passage and a first exhaust passage, and a
second cylinder group with a second air-intake passage and a second
exhaust passage. The power source may further include a first
forced-induction system in fluid communication with the first
air-intake passage, and a second forced-induction system in fluid
communication with the second air-intake passage. A catalyst may be
disposed downstream of the fuel-supply device to convert at least a
portion of the exhaust stream in the first exhaust passage into
ammonia.
Inventors: |
Robel; Wade J.; (Peoria,
IL) ; Driscoll; James Joshua; (Dunlap, IL) ;
Easley; William L. JR.; (West Peoria, IL) ;
Roozenboom; Stephan D.; (Washington, IL) |
Correspondence
Address: |
CATERPILLAR/FINNEGAN, HENDERSON, L.L.P.
901 New York Avenue, NW
WASHINGTON
DC
20001-4413
US
|
Family ID: |
38556856 |
Appl. No.: |
11/496376 |
Filed: |
July 31, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11412834 |
Apr 28, 2006 |
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11496376 |
Jul 31, 2006 |
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10982921 |
Nov 8, 2004 |
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11412834 |
Apr 28, 2006 |
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Current U.S.
Class: |
60/605.1 ;
60/299 |
Current CPC
Class: |
F01N 3/2073 20130101;
Y02T 10/144 20130101; F02B 37/007 20130101; F02D 41/1443 20130101;
F01N 2610/02 20130101; F01N 2240/25 20130101; F01N 13/011 20140603;
Y02T 10/12 20130101 |
Class at
Publication: |
060/605.1 ;
060/299 |
International
Class: |
F01N 3/10 20060101
F01N003/10 |
Goverment Interests
U.S. GOVERNMENT RIGHTS
[0002] This invention was made with government support under the
terms of Contract No. DE-FC05-00OR22806 awarded by the Department
of Energy. The government may have certain rights in this
invention.
Claims
1. A power source for use with selective catalytic reduction
systems for exhaust-gas purification, comprising: a first cylinder
group with a first air-intake passage and a first exhaust passage;
a second cylinder group with a second air-intake passage and a
second exhaust passage; a first forced-induction system in fluid
communication with the first air-intake passage; a second
forced-induction system in fluid communication with the second
air-intake passage; and a catalyst disposed downstream of the first
cylinder group to convert at least a portion of the exhaust stream
in the first exhaust passage into ammonia.
2. The power source of claim 1, further including a valve for
controlling the flow of air into the first air-intake passage.
3. The power source of claim 1, further including a fuel-supply
device configured to supply fuel into the first exhaust
passage.
4. The power source of claim 3, wherein an exhaust stream in the
first exhaust passage is lean upstream from the fuel-supply
device.
5. The power source of claim 4, wherein the exhaust stream in the
first exhaust passage is rich downstream from the fuel-supply
device.
6. The power source of claim 1, wherein the first forced-induction
system and second forced-induction system include
turbochargers.
7. The power source of claim 1, wherein the second exhaust passage
includes an oxidation catalyst.
8. The power source of claim 1, wherein the first exhaust passage
and the second exhaust passage are fluidly connected downstream
from the fuel-supply device to form a merged exhaust passage.
9. The power source of claim 8, further including a catalyst
disposed in the merged exhaust passage and configured to facilitate
a reaction between ammonia and NOx to at least partially remove NOx
from the merged exhaust passage.
10. A method of operating a power source for use with selective
catalytic reduction systems for exhaust-gas purification,
comprising: supplying air through a first air-intake passage to a
first cylinder group including one or more cylinders using a first
turbocharger; supplying fuel to the one or more cylinders of the
first cylinder group; supplying air through a second air-intake
passage to a second cylinder group including at least two cylinders
using a second turbocharger; supplying fuel to the cylinders of the
second cylinder group; and controlling the flow of air and fuel to
the cylinders of the first and second cylinder group to produce a
substantially equal power output in each of the cylinders of both
the first and second cylinder group.
11. The method of claim 10, further including supplying a first
exhaust stream from the first cylinder group to a first exhaust
passage in fluid communication with the one or more cylinders of
the first cylinder group, wherein the at least a portion of the
first exhaust stream includes NOx.
12. The method of claim 11, further including converting at least a
portion of the first exhaust stream into ammonia.
13. The method of claim 12, further including using the fuel-supply
device to make the first exhaust stream rich downstream of the
fuel-supply device.
14. The method of claim 12, further including merging the exhaust
stream of the first exhaust passage with the exhaust stream of the
second exhaust passage to form a merged exhaust stream.
15. The method of claim 14, further including exposing the merged
exhaust stream to a catalyst configured to facilitate a reaction
between ammonia and NOx; and at least partially removing NOx from
the merged exhaust stream.
16. A machine for use with selective catalytic reduction systems
for exhaust-gas purification, comprising: a first cylinder group
with a first air-intake passage and a first exhaust passage; a
second cylinder group with a second air-intake passage and a second
exhaust passage; a first forced-induction system in fluid
communication with the first air-intake passage; a second
forced-induction system in fluid communication with the second
air-intake passage; an engine control unit configured to control
the flow of air and fuel into each of the cylinders of the first
and second cylinder groups to produce substantially equal power
output from each of the cylinders of the first and second cylinder
groups; a catalyst disposed downstream of the first cylinder group
to convert at least a portion of the exhaust stream in the first
exhaust passage into ammonia; a merged exhaust passage downstream
of the catalyst and in fluid communication with the first exhaust
passage and second exhaust passage; and a NOx-reducing catalyst in
fluid communication with the merged exhaust passage.
17. The power source of claim 16, wherein the first and second
cylinders are diesel cylinders.
18. The power source of claim 16, wherein the first and second
cylinders are natural gas cylinders.
19. The power source of claim 16 wherein the first and second
cylinders are gasoline cylinders.
20. The power source of claim 16, wherein the first
forced-induction system and second forced-induction system include
turbochargers.
Description
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 11/412,834, filed Apr. 28, 2006, which is a
continuation-in-part of U.S. patent application Ser. No.
10/982,921, filed Nov. 8, 2004, both of which are hereby
incorporated by reference.
TECHNICAL FIELD
[0003] This disclosure pertains generally to exhaust-gas
purification systems for engines, and more particularly, to
selective catalytic reduction systems with on-board ammonia
production.
BACKGROUND
[0004] Selective catalytic reduction (SCR) provides a method for
removing nitrogen oxides (NOx) emissions from fossil fuel powered
systems for engines, factories, and power plants. During SCR, a
catalyst facilitates a reaction between exhaust-gas ammonia and NOx
to produce water and nitrogen gas, thereby removing NOx from the
exhaust gas.
[0005] The ammonia that is used for the SCR system may be produced
during the operation of the NOx-producing system or may be stored
for injection when needed. Because of the high reactivity of
ammonia, storage of ammonia can be hazardous. Further, on-board
production of ammonia can be costly and may require specialized
equipment.
[0006] One method of on-board ammonia production for an engine is
disclosed in U.S. Pat. No. 6,047,542, issued to Kinugasa on Apr.
11, 2000 (hereinafter the '542 patent). The method includes the use
of multiple cylinder groups for purifying exhaust gas. In the
method of the '542 patent, the exhaust gas of one cylinder group
may be made rich by controlling the amount of fuel injected into
the cylinder group. The rich exhaust gas of this cylinder group may
then be passed over an ammonia-synthesizing catalyst to convert a
portion of the NOx in the exhaust gas into ammonia. The exhaust gas
and ammonia of the first cylinder group are then combined with the
exhaust gas of a second cylinder group and passed through an SCR
catalyst where the ammonia reacts with NOx to produce nitrogen gas
and water.
[0007] While the method of the '542 patent may reduce NOx from an
exhaust stream through use of on-board ammonia production, the
method of the '542 patent has several drawbacks. For example, an
engine may function less efficiently and with lower power output
when rich combustion occurs in one cylinder group. Furthermore,
using the method of the '542 patent, it may be more difficult to
provide adequate and controlled air intake to both cylinder groups,
and the two cylinder groups, operating as described in the '542
patent, may cause significant engine vibration.
[0008] The present disclosure is directed at overcoming one or more
of the problems or disadvantages in the prior art.
SUMMARY OF THE INVENTION
[0009] A first aspect of the present disclosure includes a power
source for use with selective catalytic reduction systems for
exhaust-gas purification. The power source may comprise a first
cylinder group with a first air-intake passage and a first exhaust
passage, and a second cylinder group with a second air-intake
passage and a second exhaust passage. The power source may further
include a first forced-induction system in fluid communication with
the first air-intake passage, and a second forced-induction system
in fluid communication with the second air-intake passage. A
catalyst may be disposed downstream of the first cylinder group to
convert at least a portion of the exhaust stream in the first
exhaust passage into ammonia.
[0010] A second aspect of the present disclosure includes a method
of operating a power source for use with selective catalytic
reduction systems for exhaust-gas purification. The method may
include supplying air through a first air-intake passage to a first
cylinder group including one or more cylinders using a first
turbocharger and supplying fuel to the one or more cylinders of the
first cylinder group. The method may further include supplying air
through a second air-intake passage to a second cylinder group
including at least two cylinders using a second turbocharger and
supplying fuel to the cylinders of the second cylinder group. The
flow of air and fuel to the cylinders of the first and second
cylinder group may be controlled to produce a substantially equal
power output in each of the cylinders of both the first and second
cylinder group.
[0011] A third aspect of the present disclosure includes a power
source for use with selective catalytic reduction systems for
exhaust-gas purification. The power source may comprise a first
cylinder group with a first air-intake passage and a first exhaust
passage, and a second cylinder group with a second air-intake
passage and a second exhaust passage. The power source may further
include a first forced-induction system in fluid communication with
the first air-intake passage, and a second forced-induction system
in fluid communication with the second air-intake passage. An
engine control unit may be configured to control the flow of air
and fuel into each of the cylinders of the first and second
cylinder groups to produce substantially equal power output from
each of the cylinders of the first and second cylinder groups, and
a catalyst may be disposed downstream of the first cylinder group
to convert at least a portion of the exhaust stream in the first
exhaust passage into ammonia. A merged exhaust passage may be
formed downstream of the catalyst and may be in fluid communication
with the first exhaust passage and second exhaust passage. A
NOx-reducing catalyst may be placed in fluid communication with the
merged exhaust passage.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate exemplary
embodiments of the disclosure and, together with the written
description, serve to explain the principles of the disclosed
system. In the drawings:
[0013] FIG. 1 provides a schematic diagram of a power source
according to an exemplary disclosed embodiment.
[0014] FIG. 2 provides a diagrammatic representation of first and
second cylinder groups according to an exemplary disclosed
embodiment.
[0015] FIG. 3 provides a schematic diagram of first and second
cylinder groups according to an exemplary disclosed embodiment.
[0016] FIG. 4 provides a chart of relative power outputs of
multiple cylinders, as shown in FIG. 2, at three distinct times
according to an exemplary embodiment.
[0017] FIG. 5 provides a schematic representation of a power source
according to another exemplary disclosed embodiment.
[0018] FIG. 6A provides a schematic representation of an exhaust
passage according to an exemplary disclosed embodiment.
[0019] FIG. 6B provides a schematic representation of an exhaust
passage according to another exemplary disclosed embodiment.
[0020] FIG. 6C provides a schematic representation of an exhaust
passage according to another exemplary disclosed embodiment.
[0021] FIG. 7A provides a schematic representation of an exhaust
system configuration according to an exemplary disclosed
embodiment.
[0022] FIG. 7B provides a schematic representation of an exhaust
system configuration according to another exemplary disclosed
embodiment.
[0023] FIG. 8 provides a schematic representation of a power source
according to another exemplary disclosed embodiment.
DETAILED DESCRIPTION
[0024] FIG. 1 provides a schematic representation of a machine 10
of the present disclosure including a power source 12. Power source
12 may include a first cylinder group 14 and a second cylinder
group 16. First cylinder group 14 may be fluidly connected to a
first air-intake passage 18 and a first exhaust passage 20. Second
cylinder group 16 may be fluidly connected to a second air-intake
passage 22 and a second exhaust passage 24. In one embodiment,
first air-intake passage 18 is fluidly isolated from second
air-intake passage 22.
[0025] The operation of engine cylinders may be dependant on the
ratio of air to fuel-vapor that is injected into the cylinders
during operation. The air to fuel-vapor ratio is often expressed as
a lambda value, which is derived from the stoichiometric air to
fuel-vapor ratio. The stoichiometric air to fuel-vapor ratio is the
chemically correct ratio for combustion to take place. A
stoichiometric air to fuel-vapor ratio may be considered to be
equivalent to a lambda value of 1.0.
[0026] Engine cylinders may operate at non-stoichiometric air to
fuel-vapor ratios. An engine cylinder with a lower air to
fuel-vapor ratio has a lambda less than 1.0 and is said to be rich.
An engine cylinder with a higher air to fuel-vapor ratio has a
lambda greater than 1.0 and is said to be lean.
[0027] Lambda may affect cylinder NOx emissions and fuel
efficiency. A lean-operating cylinder may have improved fuel
efficiency compared to a cylinder operating under stoichiometric or
rich conditions. However, lean operation may increase NOx
production or may make elimination of NOx in the exhaust gas
difficult.
[0028] The cylinders of first cylinder group 14 and/or second
cylinder group 16 may include a variety of suitable engine cylinder
types. For example, suitable engine types may include diesel engine
cylinders, natural gas cylinders, or gasoline cylinders. The
specific cylinder type may be selected based on the specific
application, desired power output, available fuel infrastructure,
and/or any other suitable factor. For example, natural gas engines
may be selected for some engine types, such as generator sets.
Diesel engines may be selected for on-highway trucks. However, as
the available fuel infrastructure, fuel costs, and emission
standards change, different engine types may be selected for any
application.
[0029] SCR systems provide a method for decreasing exhaust-gas NOx
emissions through the use of ammonia. In an exemplary embodiment of
the present disclosure, engine NOx generated by lean combustion in
first cylinder group 14 may be converted into ammonia. This ammonia
may be used with an SCR system to remove NOx produced as a
byproduct of fuel combustion in power source 12.
[0030] In one embodiment, power source 12 of the present disclosure
may include an ammonia-producing catalyst 26 that may be configured
to convert at least a portion of the exhaust-gas stream from first
cylinder group 14 into ammonia. This ammonia may be produced by a
reaction between NOx and other substances in the exhaust-gas stream
from first cylinder group 14. For example, NOx may react with a
variety of other combustion byproducts to produce ammonia. These
other combustion byproducts may include, for example, H.sub.2
(hydrogen gas), C.sub.3H.sub.6 (propene), or CO (carbon
monoxide).
[0031] Ammonia-producing catalyst 26 may be made from a variety of
materials. In one embodiment, ammonia-producing catalyst 26 may
include at least one of platinum, palladium, rhodium, iridium,
copper, chrome, vanadium, titanium, iron, or cesium. Combinations
of these materials may be used, and the catalyst material may be
chosen based on the type of fuel used, the air to fuel-vapor ratio
desired, or for conformity with environmental standards.
[0032] Lean operation of first cylinder group 14 may allow
increased NOx production as compared to stoichiometric or rich
operation of first cylinder group 14. Further, the efficiency of
conversion of NOx to ammonia by ammonia-producing catalyst 26 may
be improved under rich conditions. Therefore, to increase ammonia
production, engine cylinders may be operated under lean conditions
in order to produce a NOx-containing exhaust gas, and fuel may be
supplied to this NOx-containing exhaust gas to produce a rich,
NOx-containing exhaust gas that can be used to produce ammonia by
ammonia-producing catalyst 26.
[0033] First cylinder group 14 may include one or more cylinders,
and second cylinder group 16 may include at least two cylinders.
For example, first cylinder group 14 may include between one and
ten cylinders, and second cylinder group 16 may include between two
and twelve cylinders. In one embodiment, first cylinder group 14
may include only one cylinder, and second cylinder group 16 may
include five cylinders. In another embodiment, first cylinder group
14 may include one cylinder, and second cylinder group 16 may
include seven cylinders. In another embodiment, first cylinder
group 14 may include one cylinder, and second cylinder group 16 may
include eleven cylinders. The number of cylinders in first cylinder
group 14 and the number of cylinders in second cylinder group 16
may be selected based on a desired power output to be produced by
power source 12.
[0034] In one embodiment, first cylinder group 14 may operate with
a lean air-to-fuel ratio within the one or more cylinders of first
cylinder group 14. The one or more cylinders of first cylinder
group 14, operating with a lean air to fuel-vapor ratio, may
produce a lean exhaust-gas stream that contains NOx. The lean,
NOx-containing exhaust-gas stream may flow into first exhaust
passage 20, which may be fluidly connected with the one or more
cylinders of first cylinder group 14.
[0035] In order to produce the rich conditions that favor
conversion of NOx to ammonia, a fuel-supply device 28 may be
configured to supply fuel into first exhaust passage 20. In one
embodiment, a lean, NOx-containing exhaust-gas stream may be
delivered to first exhaust passage 20, and fuel-supply device 28
may be configured to supply fuel into first exhaust passage 20,
thereby making the exhaust-gas stream rich. In one embodiment, the
exhaust-gas stream in first exhaust passage 20 may be lean upstream
of fuel-supply device 28 and rich downstream of fuel-supply device
28.
[0036] First exhaust passage 20 may fluidly communicate with second
exhaust passage 24 at a point downstream of fuel-supply device 28
to form a merged exhaust passage 30. Merged exhaust passage 30 may
contain a mixture of an exhaust-gas stream produced by second
cylinder group 16 and an ammonia-containing, exhaust-gas stream
produced by ammonia-producing catalyst 26 in first exhaust passage
20.
[0037] A NOx-reducing catalyst 32 may be disposed in merged exhaust
passage 30. In one embodiment, NOx-reducing catalyst 32 may
facilitate a reaction between ammonia and NOx to at least partially
remove NOx from the exhaust-gas stream in merged exhaust passage
30. For example, NOx-reducing catalyst 32 may facilitate a reaction
between ammonia and NOx to produce nitrogen gas and water, among
other reaction products.
[0038] Power source 12 may include forced-induction systems to
increase power output and/or control the air to fuel-vapor ratios
within the cylinders of first cylinder group 14 or second cylinder
group 16. Forced-induction systems may include, for example,
turbochargers and/or superchargers. In one embodiment, a first
forced-induction system 34 may be operably connected with first
air-intake passage 18, and a second forced-induction system 36 may
be operably connected with second air-intake passage 22.
[0039] In one embodiment, first forced-induction system 34 or
second forced-induction system 36 may include a turbocharger. The
turbocharger may utilize the exhaust gas in first exhaust passage
20 or second exhaust passage 24 to generate power for a compressor,
and this compressor may provide additional air to first air-intake
passage 18 or second air-intake passage 22. Therefore, if first
forced-induction system 34 or second forced-induction system 36
includes a turbocharger, the turbocharger may be operably connected
with both an exhaust passage 20, 24 and an air-intake passage 18,
22, as shown in FIG. 1.
[0040] In one embodiment, ammonia-producing catalyst 26 may be
positioned downstream of first forced induction system 34. The
exhaust stream in first exhaust passage 20 may be cooler downstream
of first forced-induction system 34 than upstream of first
forced-induction system 34. Ammonia-producing catalyst 26 may
function more efficiently when exposed to a cooler exhaust-gas
downstream of first forced-induction system 34.
[0041] In one embodiment, first forced-induction system 34 or
second forced-induction system 36 may include a supercharger. A
supercharger may derive its power from a belt that connects
directly to an engine. Further, superchargers do not need to be
connected with an exhaust stream. Therefore, if first
forced-induction system 34 or second forced-induction system 36
includes a supercharger, the supercharger may be operably connected
with first air-intake passage 18 or second air-intake passage 22,
but the supercharger need not be operably connected with first
exhaust passage 20 or second exhaust passage 24.
[0042] In an alternative embodiment, first air-intake passage 18 or
second air-intake passage 22 may be naturally aspirated. A
naturally aspirated air-intake passage may include no
forced-induction system. Alternatively, an air-intake passage may
include a forced-induction system, but the forced-induction system
may be turned on and off based on demand. For example, when
increased airflow is needed, first forced-induction system 34 or
second forced-induction system 36 may be turned on to supply
additional air to first air-intake passage 18 and/or second
air-intake passage 22. When lower air-intake is needed, such as
when little power is needed from power source 12, first air-intake
passage 18 and/or second air intake passage 22 may be naturally
aspirated. In one embodiment, second air-intake passage 22 may be
operably connected with second forced-induction system 36, and
first air-intake passage 18 may be naturally aspirated.
[0043] In one embodiment, second exhaust passage 24 may include an
oxidation catalyst 37. NOx may include several oxides of nitrogen
including nitric oxide (NO) and nitrogen dioxide (NO.sub.2), and
NOx-reducing catalyst 32 may function most effectively with a ratio
of NO:NO.sub.2 of about 1:1. Oxidation catalyst 37 may be
configured to control a ratio of NO:NO.sub.2 in second exhaust
passage 24. Further, by controlling a ratio of NO:NO.sub.2 in
second exhaust passage 24, oxidation catalyst 37 may also control a
ratio of NO:NO.sub.2 in merged exhaust passage 30.
[0044] A variety of additional catalysts and/or filters may be
included in first-exhaust passage 20 and/or second exhaust passage
24. These catalysts and filters may include particulate filters,
NOx traps, and/or three-way catalysts. In one embodiment,
first-exhaust passage 20 and/or second exhaust passage 24 may
include, for example, one or more diesel particulate filters.
[0045] In one embodiment of the present disclosure, the power
outputs of the one or more cylinders of first cylinder group 14 may
be different than the power outputs of the cylinders of second
cylinder group 16. To avoid potential vibration that may result
from unbalanced cylinder operation, the stroke cycles of one or
more cylinders of first cylinder group 14 may be matched with the
stoke cycles of one or more cylinders of second cylinder group
16.
[0046] In one embodiment shown in FIG. 2, the stroke cycle of one
or more cylinders of first cylinder group 14 may be matched with
the stroke cycle of one or more cylinders of second cylinder group
16. In this embodiment, first cylinder group 14 includes only a
single cylinder 38, and second cylinder group 16 includes five
cylinders, including a cylinder 40 and all other cylinders 42, 44,
46, 48 of second cylinder group 16. Further, single cylinder 38 of
first cylinder group 14 has a stroke cycle that is matched with the
stroke cycle of cylinder 40 of second cylinder group 16. All the
other cylinders 42, 44, 46, 48 of the second cylinder group 16 may
have unique stroke cycles.
[0047] FIG. 3 illustrates the fluid communications of air-intake
passages and exhaust passages with the cylinders of FIG. 2. In this
embodiment, first air-intake passage 18 and first exhaust passage
20 may fluidly communicate with single cylinder 38 of first
cylinder group 14. Further, second air-intake passage 22 may
fluidly communicate with cylinder 40 of second cylinder group 16,
as well as all the other cylinders 42, 44, 46, 48 of second
cylinder group 16, and second air-intake passage 22 may be fluidly
isolated from first air-intake passage 18. In addition, second
exhaust passage 24 may fluidly communicate with cylinder 40 of
second cylinder group 16, as well as all the other cylinders 42,
44, 46, 48 of second cylinder group 16.
[0048] In one embodiment, the power outputs of each cylinder of
power source 12 may be controlled during operation of power source
12. FIG. 4 illustrates exemplary power outputs of each of the
cylinders of power source 12. In this embodiment, the power output
of each of the cylinders of power source 12 may be expressed as a
relative power output. The relative power output is a numeric value
multiplied by a variable, in this case (x), wherein the total power
output of power source 12 equals the number of cylinders multiplied
by the variable, x. Therefore, in the embodiment of FIG. 4, where
power source 12 includes six cylinders, the total power output of
power source 12 may be expressed as 6x.
[0049] The variable, x, may be any power value. For example, x may
be a number of horsepower (hp), watts, or foot-pounds per unit
time. If, for example, the total power output of all the cylinders
38, 40, 42, 44, 46, 48 of power source 12 equals 30 hp, then x will
equal 5 hp.
[0050] In one embodiment, illustrated at Time 1 in FIG. 4, the
relative power output of each of the cylinders of power source 12,
including single cylinder 38, cylinder 40, and all the other
cylinders 42, 44, 46, 48 of second cylinder group 16, is
approximately 1.0x. The total power output of all the cylinders 38,
40, 42, 44, 46, 48 of power source 12, therefore, equals 6x. In
this embodiment, the power output of power source 12 is distributed
equally between each of the cylinders of power source 12.
[0051] In one embodiment, illustrated at Time 2 in FIG. 4, the
relative power output of single cylinder 38 of first cylinder group
14 equals 0.25x, and the relative power output of cylinder 40 of
second cylinder group 16 equals 0.75x. Further, the relative power
output of all of the other cylinders 42, 44, 46, 48 is
approximately 1.25x, and the total power output of all the
cylinders 38, 40, 42, 44, 46, 48 of power source 12 equals 6x.
[0052] In another embodiment, illustrated at Time 3 in FIG. 4, the
relative power output of single cylinder 38 of first cylinder group
14 equals 0.25x, and the relative power output of cylinder 40 of
second cylinder group 16 equals 0.95x. Further, the relative power
output of all of the other cylinders 42, 44, 46, 48 is
approximately 1.2x, and the total power output of all the cylinders
38, 40, 42, 44, 46, 48 of power source 12 equals 6x.
[0053] The embodiments at Time 2 and Time 3 of FIG. 4 may allow
power source 12 to operate with the minimum possible vibration,
while also allowing the relative power outputs of the cylinders of
power source 12 to be changed during operation. In these
embodiments, matching of the stroke cycles of single cylinder 38
and cylinder 40 may allow these two cylinders to produce combined
power and force similar to any one of the other cylinders 42, 44,
46, 48 of second cylinder group 16. Further, the force produced by
single cylinder 38 and cylinder 40 may be balanced by the power and
force of all the other cylinders 42, 44, 46, 48 of second cylinder
group 16.
[0054] Controlling the power outputs of each of the cylinders of
power source 12 may affect ammonia production, NOx emissions,
maximum power output, and/or fuel efficiency. For example, when
increased power output is needed, all cylinders of power source 12
may operate at maximum power. In another embodiment, the power
output of any one of the one or more cylinders of first cylinder
group 14 may be less than the power output of each of the cylinders
of second cylinder group 16, as shown at Time 2 and Time 3 of FIG.
4. In this embodiment, first cylinder group 14 may produce less
power, but the operation of first cylinder group 14 may be
controlled to match ammonia production with NOx production from
second cylinder group 16.
[0055] FIG. 5 provides a schematic diagram of power source 12
according to another exemplary disclosed embodiment. As described
above, power source 12 may include first cylinder group 14 and
second cylinder group 16, wherein first cylinder group 14 may be
fluidly connected to first air-intake passage 18 and first exhaust
passage 20, and second cylinder group 16 may be fluidly connected
to second air-intake passage 22 and second exhaust passage 24.
[0056] In some embodiments, first air-intake passage 18 may be
configured to provide air having a first set of characteristics to
first cylinder group 14, and second-air intake passage 22 may be
configured to provide air having a second set of characteristics to
second cylinder group 16. Air-intake passages may be configured to
modify one or more air properties, such as, for example, air
pressure, flow rate or temperature. In particular, first air-intake
passage 18 and second air-intake passage 22 may be configured such
that air at the first set of characteristics may be different from
air at the second set of characteristics, wherein the first and
second set of characteristics may include one or more air
properties. For example, first air-intake passage 18 may include a
smaller cross-sectional area than second air-intake passage 22 to
reduce the pressure of air supplied to first cylinder group 14.
Supplying first cylinder group 14 and second cylinder group 16 with
air at different properties may permit first cylinder group 14 and
second cylinder group 16 to produce different emission levels while
producing substantially similar power outputs from each
cylinder.
[0057] In some embodiments, first air-intake passage 18 may be
fluidly connected to second air-intake passage 22, wherein first
air-intake passage 18 may include a valve 50. Valve 50 may include
any device configured to modify one or more air properties. In
particular, valve 50 may be configured to modify one or more air
properties such that air downstream of valve 50 may have a first
set of characteristics and air upstream of valve 50 may have a
second set of characteristics. For example, valve 50 may be
configured to reduce air pressure and/or flow rate downstream of
valve 50. Valve 50 may be configured to reduce air pressure within
first air-intake passage 18 relative to second air-intake passage
22 such that first cylinder group 14 may be supplied with air at a
lower pressure than air supplied to second cylinder group 16.
[0058] Valve 50 may include a throttle, an inductive venturi
aperture, or other similar device configured to modify an air
property. In some embodiments, valve 50 may be configured to
selectively modify an air property within first air-intake passage
18 during variable load operation of power source 12. For example,
valve 50 may modify an air property based on an operational
condition of power source 12, such as, engine speed or engine load.
As engine speed increases valve 50 may increase the pressure
difference between air in first air-intake passage 18 and
second-air intake passage 22 by decreasing air flow rate through
valve 50.
[0059] In some embodiments, first cylinder group 14 and second
cylinder group 16 may operate with combustion reactions at
different efficiencies. Supplying first cylinder group 14 and
second cylinder group 16 with air at different properties may
permit combustion reactions at different efficiencies within first
cylinder group 14 and second cylinder group 16. Combustion
reactions at different efficiencies may produce different
combustion products and different levels of emissions from first
cylinder group 14 and second cylinder group 16. For example,
supplying first cylinder group 14 with air at a lower pressure than
air supplied to second cylinder group 16 may permit first cylinder
group 14 to produce increased levels of NOx relative to second
cylinder group 16. Emission levels may also be affected by other
operational parameters of power source 12, such as, for example,
air to fuel-vapor ratio, valve timing, or fuel injection
timing.
[0060] During operation of power source 12, first cylinder group 14
may operate at or near stoichiometric air to fuel-vapor ratios,
wherein the lambda value is approximately 1.0, while second
cylinder group 16 may operate under leaner conditions, wherein
lambda is greater than 1.0. According to an exemplary embodiment,
valve 50 may be configured to reduce the air pressure and/or flow
rate in first air-intake passage 18 such that first cylinder group
14 may operate at lambda approximately equal to one. Operation of
first cylinder group 14 at lambda approximately equal to 1.0, or
slightly richer, may facilitate ammonia production at catalyst
26.
[0061] As discussed above, a power output of each cylinder of first
cylinder group 14 may be different than a power output of each
cylinder of second cylinder group 16. It is also contemplated that
the power outputs of the one or more cylinders of first cylinder
group 14 may be similar to the power outputs of the cylinders of
second cylinder group 16. Specifically, each cylinder of first
cylinder group 14 may operate to produce a power output similar to
each cylinder of second cylinder group 16. For example, a quantity
of fuel supplied to each cylinder of first cylinder group 14 may be
approximately equal to a quantity of fuel supplied to each cylinder
of second cylinder group 16. Also, fuel injection timing and/or
valve timing for each cylinder of first cylinder group 14 may be
varied such that the power output of each cylinder of first
cylinder group 14 may be similar to the power output of each
cylinder of second cylinder group 16. Such operating conditions may
permit power source 12 to produce substantially similar power
output from a cylinder of first cylinder group 14 and a cylinder of
second cylinder group 16 while first cylinder group 14 may operate
at approximately stoichiometric air to fuel-vapor ratio and second
cylinder group 16 may operate at leaner combustion conditions.
[0062] Power source 12 may include one or more forced-induction
systems to increase power output, as previously described. As shown
in FIG. 5, a forced-induction system 54 may be operably connected
to second air intake passage 22 and first air-intake passage 18,
wherein first air-intake passage 18 may include valve 50.
Forced-induction system 54 may include a supercharger, operably
connected to power source 12 via a belt and/or gear assembly. The
supercharger may utilize a portion of the energy produced by power
source 12 to compress air in first air-intake passage 18 and second
air-intake passage 22, thereby increasing the power output of power
source 12.
[0063] In some embodiments, forced-induction system 54 may include
a turbocharger. As described above, the turbocharger may utilize
the exhaust gas in second exhaust passage 24 and/or first exhaust
passage 20 to generate power for a compressor. The compressor may
further be configured to compress the air in first air-intake
passage 18 and second air-intake passage 22.
[0064] Various catalysts and/or filters may be included in
first-exhaust passage 20 and/or merged passage 30. Exemplary
catalysts and filters may include particulate filters, NOx traps,
and/or three-way catalysts. As described previously, first exhaust
passage 20 may include fuel-supply device 28 and/or
ammonia-producing catalyst 26 configured to facilitate ammonia
production in first exhaust passage 20. First exhaust passage 20
may also include a diesel particulate filter 27, configured to
collect solid and liquid particulate matter emissions. Diesel
particulate filter 27 may also be disposed in merged exhaust
passage 30. In addition, first exhaust passage 20 may also include
a partial oxidation catalyst 29, configured to reduce emissions of
gaseous hydrocarbons and liquid hydrocarbon particles.
[0065] FIGS. 6A-6C provide schematic diagrams of first exhaust
passage 20 according to several exemplary disclosed embodiments. As
well as various catalysts and/or filters, first exhaust passage 20
may include a turbo-compound 52 configured to provide additional
energy to machine 10. Turbo-compound 52 may be configured to
convert energy in exhaust gases of power source 12 into rotational
energy that may be added to power source 12.
[0066] As described above, exhaust gases in first exhaust passage
20 and/or second exhaust passage 24 may be used to drive a
conventional turbocharger. Following passage through the
conventional turbocharger, exhaust gases may then be directed into
turbo-compound 52 to spin a turbine. The turbine may be configured
to provide additional power to power source 12. For example, the
revolutions of the turbine may be stepped down by mechanical gears
and/or a hydraulic coupling to drive a shaft mechanically connected
to power source 12.
[0067] As shown in FIG. 6A, turbo-compound 52 may be placed at any
position within first exhaust passage 20. Specifically,
turbo-compound 52 may be located upstream or downstream of diesel
particulate filter 27, partial oxidation catalyst 29 and/or
ammonia-producing catalyst 26. Further, first exhaust passage 20
may or may not include fuel-supply device 28 upstream or downstream
of diesel particulate filter 27.
[0068] In some embodiments, first exhaust passage 20 may include
additional and/or fewer components. For example as shown in FIG.
6B, first exhaust passage 20 may include fuel-supply device 28 and
ammonia-producing catalyst 26. First exhaust passage 20 may also
include turbo-compound 52 located upstream or downstream of
fuel-supply device 28 and ammonia-producing catalyst 26.
[0069] First exhaust passage 20 may include one or more branched
configurations. As shown in FIG. 6C, first exhaust passage 20 may
split into two sub-passages, a first exhaust sub-passage 20' and a
second exhaust sub-passage 20''. Each sub-passage may include at
least one of the various catalysts, filters and/or turbo-compound
52. Specifically, first exhaust sub-passage 20' may include
fuel-supply device 28 and/or partial oxidation catalyst 29. First
exhaust passage 20 may include diesel particulate filter 27
upstream or downstream of each sub-passage. It is also contemplated
that turbo-compound 52 may be positioned anywhere within first
exhaust passage 20, first exhaust sub-passage 20', or second
exhaust sub-passage 20''.
[0070] FIGS. 7A-7B provide schematic diagrams of one or more
exhaust passages according to several exemplary disclosed
embodiments. As discussed above, first-exhaust passage 20, second
exhaust passage 24 and/or merged passage 30 may include various
catalysts and/or filters. For example, merged passage 30 may
include an ammonia-reducing catalyst 31 configured to remove
ammonia from the exhaust gas to substantially prevent ammonia
release to the atmosphere.
[0071] As shown in FIG. 7A, turbo-compound 52 may be placed at any
suitable position within first exhaust passage 20 and/or merged
passage 30. Specifically, turbo-compound 52 may be located upstream
or downstream of ammonia-producing catalyst 26 in first exhaust
passage 20. Turbo-compound 52 may also be located upstream of
diesel particulate filter 27 in merged passage 30.
[0072] In some embodiments, first exhaust passage 20, second
exhaust passage 24 and/or merged passage 30 may include additional
and/or fewer components. For example as shown in FIG. 7B, first
exhaust passage 20 may include diesel particulate filter 27 and
ammonia-producing catalyst 26 and second exhaust passage 24 may
include diesel particulate filter 27. Further, merged passage 30
may include NOx-reducing catalyst 32 and ammonia-reducing catalyst
31. Turbo-compound 52 may also be located upstream or downstream of
diesel particulate filter 27 in first exhaust passage 20, upstream
of NOx-reducing catalyst 32 in merged passage 30, or downstream of
diesel particulate filter 27 in second exhaust passage 24.
[0073] FIG. 8 provides a schematic representation of a machine 10',
including a power source 12 according to another exemplary
disclosed embodiment. This embodiment is similar to the embodiment
of FIG. 1, wherein power source 12 may include a first cylinder
group 14 and a second cylinder group 16. First cylinder group 14
may be fluidly connected to a first air-intake passage 18 and a
first exhaust passage 20. Second cylinder group 16 may be fluidly
connected to a second air-intake passage 22 and a second exhaust
passage 24.
[0074] Machine 10' further includes first and second
forced-induction systems 34, 36 (e.g. turbochargers). First and
second forced-induction systems 34, 36 may be configured to
separately supply air to first air-intake passage 18 and second
air-intake passage 22. In some embodiments, the separate
forced-induction systems 34, 36 may allow rapid and accurate
control of the power output within each of the cylinders of first
cylinder group 14 and second cylinder group 16.
[0075] The power output of each of the cylinders of first cylinder
group 14 and second cylinder group 16 may be controlled by a number
of different factors, including, for example, air-to-fuel ratio,
absolute amounts of air and fuel in the cylinders, and/or injection
timing. In some embodiments, power source 12 may include an engine
control unit 33, configured to control the power output of each of
the cylinders of first cylinder group 14 and second cylinder group
16.
[0076] Control unit 33 may include a variety of suitable machine
electronic control units. For example, control unit 33 may include
one or more microprocessors, a memory unit, a data storage device,
a communications hub, and/or other components known in the art. It
is contemplated that control unit 33 may be integrated within a
general control system capable of controlling various functions of
power source 12 and/or other components of machine 10. Further,
control unit may determine various machine operational parameters
and deliver output signals to effect desired operation by power
source 12 or any other exhaust system or machine components.
[0077] In some embodiments, control unit 33 may control the amount
and timing of air and/or fuel supplied to the cylinders of power
source 12. For example, control unit 33 may control the operation
of turbochargers 34, 36 to control cylinder air-fuel ratios. In
addition, first and or second intake passage 18, 22 may further
include suitable valves 35 or other systems for controlling the
supply of air through from turbochargers 34, 36 or an intake
manifold.
[0078] In addition, control unit 33 may control the amount and
timing of fuel supplied to cylinders of power source 12. For
example, first and second cylinder groups 14, 16 may include fuel
supply systems, such as fuel injectors 15, 17. Control unit 33 may
be configured to control fuel injection to control the power output
and emissions from each cylinder of first and second cylinder
groups 14, 16.
[0079] In some embodiments, control unit 33 may be configured to
produce a substantially equal power output from each of the
cylinders of first and second cylinder groups 14, 16 to control
power source vibration. Further, while producing substantially
equal power outputs from each cylinder, control unit may effect
production of different exhaust gas compositions. For example, as
noted previously, it may be desirable to produce a higher amount of
NOx in first cylinder group 14, thereby allowing NOx to be
converted to ammonia at a downstream ammonia-producing catalyst
26.
[0080] As noted previously, the amount of NOx produced by first
cylinder group 14 may be affected by a number of factors. For
example, in some embodiments, first cylinder group 14 may be run
lean, and a fuel supply device 28 may be positioned downstream of
first cylinder group 14 to enrich the exhaust gas, thereby
facilitating ammonia production at ammonia-producing catalyst 26.
In other embodiments, first cylinder group 14 may be run at
stoichiometric or slightly rich air-to-fuel ratios to increase
power output and/or match the power output of the cylinders of
second cylinder group. Further, in some embodiments, a premixed
engine type, such as a natural gas engine, may be selected. Under
some conditions, premixed fuels will allow a higher level of NOx
production without excess soot formation. Any suitable operating
condition or engine type may be selected as long as the power
output from each cylinder in first cylinder group 14 and second
cylinder group 16 is approximately equal.
INDUSTRIAL APPLICABLITY
[0081] The present disclosure provides an exhaust-gas purification
system including a power source with on-board ammonia production.
This purification system may be useful in all engine types that
produce NOx emissions.
[0082] The power source of the present disclosure provides a method
for improved control of ammonia production, power output, and NOx
emissions. The power source includes first and second cylinder
groups with fluidly isolated air-intake passages. The fluidly
isolated air-intake passages may be connected to separate
forced-induction systems to rapidly change air-intake in either one
or both of the cylinder groups. Further, in order to increase
ammonia production, one cylinder group may operate under lean
conditions, and fuel may be injected into the NOx-containing
exhaust gas to produce a rich, NOx-containing exhaust that may be
converted to ammonia for use with SCR systems.
[0083] In addition, the present disclosure provides a method for
reducing engine vibrations due to differences in power output of
individual engine cylinders. The method includes matching the
cylinder stroke cycles of two or more cylinders so that these
cylinders may function as a single cylinder. Matching of stroke
cycles in this way may reduce engine vibrations by balancing power
output and vibrations of each engine cylinder. This method may also
allow low engine vibration, while operating the engine at different
load levels.
[0084] The present disclosure also provides a method to produce
similar power output by each cylinder of first cylinder group 14
and second cylinder group 16. For example, air flow to first
air-intake passage 18 may be reduced relative to air flow to second
air-intake passage 22 using valve 50 and/or first forced-induction
system 34 and second forced-induction system 36. Reduced air flow
and injection of similar fuel quantities to each cylinder of power
source 12 may permit first cylinder group 14 to operate at lambda
approximately equal to one and second cylinder group 16 to operate
at leaner combustion conditions where lambda is greater than one.
Such operating conditions may result in similar power output from
each cylinder of power source 12 while maintaining higher NOx
emissions from first cylinder group 14. Variation of injection
timing and/or cam timing may also permit each cylinder of power
source 12 to produce similar power output while maintaining
appropriate emission levels. In addition, the present disclosure
provides systems and methods for rapidly and accurately controlling
the flow of air an fuel into separate cylinder groups. Theses
methods may include the use of separate turbochargers for each
cylinder group, or providing a separate valve system for
controlling the flow of turbocharged air to each cylinder group.
The separate forced-induction systems and/or turbocharger flow
control systems may allow rapid and accurate control of the power
output from each of the cylinder, even when using conventional
drive shaft designs. The rapid control of the power output from the
cylinders of the first and second cylinder group will minimize
engine vibrations, while allowing different emissions from the
separate cylinder groups.
[0085] Another advantage of the present disclosure may be the
enhanced fuel efficiency of power source 12. Specifically,
additional energy may be extracted from the fuel by power source 12
through the use of turbo-compound 52. Turbo-compound 52 may permit
additional energy contained within exhaust gases to be converted
into additional mechanical energy provided by power source 12.
[0086] It will be apparent to those skilled in the art that various
modifications and variations can be made in the disclosed systems
and methods without departing from the scope of the disclosure.
Other embodiments of the disclosed systems and methods will be
apparent to those skilled in the art from consideration of the
specification and practice of the embodiments disclosed herein. It
is intended that the specification and examples be considered as
exemplary only, with a true scope of the disclosure being indicated
by the following claims and their equivalents.
* * * * *