U.S. patent application number 14/440739 was filed with the patent office on 2016-06-02 for conversion of nox in exhaust gas.
The applicant listed for this patent is INTERNATIONAL ENGINE INTELLECTUAL PROPERTY COMPANY, LLC. Invention is credited to Paul Boon Charintranond, Adam C. Lack, Michael James Miller, Randall R. Roepke, Navtej Singh.
Application Number | 20160153333 14/440739 |
Document ID | / |
Family ID | 50627911 |
Filed Date | 2016-06-02 |
United States Patent
Application |
20160153333 |
Kind Code |
A1 |
Lack; Adam C. ; et
al. |
June 2, 2016 |
CONVERSION OF NOx IN EXHAUST GAS
Abstract
A quantity of ammonia being consumed within an exhaust system of
an internal combustion engine to reduce NOx in exhaust passing
through the exhaust system by chemical reactions enabled by an SCR
catalyst is calculated by processing, in accordance with an
algorithm, certain data including data indicative of a quantity of
NOx in exhaust upstream of where ammonia is being introduced into
the exhaust system, data indicative of a quantity of NOx in exhaust
downstream of the SCR catalyst, and data indicative of exhaust
flow.
Inventors: |
Lack; Adam C.; (Boulder,
CO) ; Singh; Navtej; (Arlington Heights, IL) ;
Roepke; Randall R.; (Chicago, IL) ; Miller; Michael
James; (Mt. Prospect, IL) ; Charintranond; Paul
Boon; (Chicago, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERNATIONAL ENGINE INTELLECTUAL PROPERTY COMPANY, LLC |
Lisle |
IL |
US |
|
|
Family ID: |
50627911 |
Appl. No.: |
14/440739 |
Filed: |
July 16, 2013 |
PCT Filed: |
July 16, 2013 |
PCT NO: |
PCT/US13/50616 |
371 Date: |
May 5, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61722338 |
Nov 5, 2012 |
|
|
|
Current U.S.
Class: |
60/276 |
Current CPC
Class: |
F01N 2900/0601 20130101;
F01N 2610/02 20130101; F01N 11/00 20130101; F01N 2550/05 20130101;
F01N 2900/1622 20130101; Y02T 10/47 20130101; Y02T 10/40 20130101;
F01N 2560/026 20130101; F01N 11/007 20130101; F01N 3/208 20130101;
Y02T 10/24 20130101; F01N 2900/1402 20130101; F01N 2550/02
20130101; Y02T 10/12 20130101 |
International
Class: |
F01N 3/20 20060101
F01N003/20; F01N 11/00 20060101 F01N011/00 |
Claims
1. An internal combustion engine comprising: combustion chambers
within which fuel is combusted to operate the engine; an intake
system through which air for supporting combustion is introduced
into the combustion chambers; an exhaust system through which
exhaust resulting from combustion in the combustion chambers passes
to atmosphere and which comprises an SCR catalyst; an ammonia
delivery system for introducing ammonia into the exhaust system
upstream of the SCR catalyst for entrainment with exhaust flow
toward the SCR catalyst; and a processor for processing certain
data including data indicative of a quantity of NOx in exhaust
upstream of where ammonia is being introduced into the exhaust
system, data indicative of a quantity of NOx in exhaust downstream
of the SCR catalyst, and data indicative of exhaust flow, in
accordance with an algorithm to estimate a quantity of ammonia
consumed by chemical reactions which are enabled by the SCR
catalyst to reduce NOx to N.sub.2 and H.sub.2O.
2. The engine set forth in claim 1 including a downstream NOx
sensor providing the data indicative of a quantity of NOx in
exhaust downstream of the SCR catalyst.
3. The engine set forth in claim 2 including an upstream NOx sensor
providing the data indicative of a quantity of NOx in exhaust
upstream of where ammonia is being introduced into the exhaust
system.
4. The engine set forth in claim 3 including a diesel oxidation
catalyst in the exhaust system upstream of the SCR catalyst, and in
which the upstream NOx sensor is disposed to indicate a quantity of
NOx in the exhaust upstream of the diesel oxidation catalyst.
5. The engine set forth in claim 1 in which the algorithm comprises
a division calculation for dividing data indicative of a quantity
of NOx in exhaust downstream of the SCR catalyst by data indicative
of a quantity of NOx in exhaust upstream of where ammonia is being
introduced into the exhaust system, a subtraction calculation for
subtracting the division calculation from unity, and a
multiplication calculation for multiplying the subtraction
calculation a) by a quantity of ammonia which would have been
consumed according to one or more chemical reactions in which at
least ammonia and NOx are reactants in order to reduce NOx to the
subtraction calculation, and b) by data indicative of exhaust flow
through the SCR catalyst.
6. The engine set forth in claim 1 in which the chemical reactions
comprise one or more of: 4NO+4NH3+O2.fwdarw.4N2+6H2O
NO+NO2+2NH3.fwdarw.2N2+3H2O 6NO2+8NH3.fwdarw.7N2+12H2O.
7. The engine set forth in claim 5 in which the algorithm further
comprises a conversion calculation for converting the
multiplication calculation to desired units of ammonia
consumption.
8. A method for estimating a quantity of ammonia being consumed by
chemical reactions which are enabled by an SCR catalyst within an
exhaust system of an internal combustion engine to reduce NOx in
exhaust passing through the exhaust system to N.sub.2 and H.sub.2O,
the method comprising: processing certain data, including data
indicative of a quantity of NOx in exhaust upstream of where
ammonia is being introduced into the exhaust system, data
indicative of a quantity of NOx in exhaust downstream of the SCR
catalyst, and data indicative of exhaust flow, in accordance with
an algorithm to estimate a quantity of ammonia consumed by chemical
reactions enabled by the SCR catalyst within the exhaust
system.
9. The method set forth in claim 8 comprising using a downstream
NOx sensor to provide the data indicative of a quantity of NOx in
exhaust downstream of the SCR catalyst.
10. The method set forth in claim 9 comprising using an upstream
NOx sensor to provide the data indicative of a quantity of NOx in
exhaust upstream of where ammonia is being introduced into the
exhaust system.
11. The method set forth in claim 9 comprising using an upstream
NOx sensor to provide the data indicative of a quantity of NOx in
exhaust upstream both of where ammonia is being introduced into the
exhaust system and of a diesel oxidation catalyst which is upstream
of the SCR catalyst in the exhaust system.
12. The method set forth in claim 8 in which the processing
comprises a division step of dividing data indicative of a quantity
of NOx in exhaust downstream of the SCR catalyst by data indicative
of a quantity of NOx in exhaust upstream of where ammonia is being
introduced into the exhaust system, a subtraction step of
subtracting a result of the division step from unity, and a
multiplication step of multiplying a result of the subtraction step
a) by a quantity of ammonia which would have been consumed
according to chemical reactions in which at least ammonia and NOx
are reactants in order to reduce NOx to the subtraction calculation
and b) by data indicative of exhaust flow through the SCR
catalyst.
13. The method set forth in claim 12 further comprising converting
a result of the multiplying step to desired units of ammonia
consumption.
14. A system for estimating a quantity of ammonia consumed by
selective catalytic reduction (SCR) of NOx in exhaust flow through
an exhaust system, the system comprising: an SCR catalyst; an
ammonia supply; an ammonia outlet through which ammonia from the
ammonia supply is introduced into the exhaust flow; a downstream
NOx sensor providing data indicative of a quantity of NOx in
exhaust flow downstream of the SCR catalyst; a data source
providing data indicative of a quantity of NOx in exhaust flow
upstream of where ammonia is being introduced into the exhaust
system; and a processor for processing data from the downstream NOx
sensor, data from the data source, and data indicative of exhaust
flow, in accordance with an algorithm to estimate a quantity of
ammonia consumed to reduce NOx to N.sub.2 and H.sub.2O by chemical
reactions enabled by the SCR catalyst.
15. The system set forth in claim 14 in which the algorithm
comprises a division calculation for dividing data provided by the
downstream NOx sensor by data provided by the data source, a
subtraction calculation for subtracting the division calculation
from unity, and a multiplication calculation for multiplying the
subtraction calculation a) by a quantity of ammonia which would
have been consumed according to one or more chemical reactions in
which at least ammonia and NOx are reactants in order to reduce NOx
to the subtraction calculation, and b) by data indicative of
exhaust flow through the SCR catalyst.
16. The system set forth in claim 14 in which the data source
comprises an upstream NOx sensor.
Description
TECHNICAL FIELD
[0001] This disclosure relates generally to Selective Catalytic
Reduction (SCR) of oxides of Nitrogen (NOx) in gaseous products of
combustion, and more particularly to a system and method for
estimating a quantity of ammonia (NH.sub.3) consumed by SCR
conversion of NOx in exhaust passing through an exhaust system of
an internal combustion engine.
BACKGROUND
[0002] One engine exhaust technology for after-treatment of engine
exhaust utilizes SCR to enable certain chemical reactions to occur
between NOx and ammonia injected into an exhaust system. Those
reactions convert NOx into Nitrogen (N.sub.2) and water (H.sub.2O),
two constituents found in abundance in earth's atmosphere. NOx and
ammonia are the only reactants in certain of those reactions while
Oxygen (O.sub.2), which may be present in the exhaust, is a third
reactant in other reactions.
[0003] Ammonia is introduced in sufficient quantity to maintain a
presence of ammonia on surfaces of the SCR catalyst where the
chemical reactions to reduce NOx take place.
SUMMARY
[0004] A quantity of ammonia introduced into the exhaust system can
be measured in various ways. However, that measurement doesn't
necessarily equate to ammonia consumed to reduce NOx. If ammonia is
being introduced in quantity which creates ammonia slip, some of
the ammonia being introduced is not consumed and instead is
exhausted into the atmosphere.
[0005] The presently disclosed subject matter relates to estimating
a quantity of ammonia actually consumed in reducing NOx to N.sub.2
and H.sub.2O.
[0006] One general aspect of the disclosed subject matter relates
to an internal combustion engine comprising combustion chambers
within which fuel is combusted to operate the engine, an intake
system through which air for supporting combustion is introduced
into the combustion chambers, an exhaust system through which
exhaust resulting from combustion in the combustion chambers passes
to atmosphere and which comprises an SCR catalyst, and an ammonia
delivery system for introducing ammonia into the exhaust system
upstream of the SCR catalyst for entrainment with exhaust flow
toward the SCR catalyst.
[0007] A processor processes certain data, including data
indicative of a quantity of NOx in exhaust upstream of where
ammonia is introduced into the exhaust system, data indicative of a
quantity of NOx in exhaust downstream of the SCR catalyst, and data
indicative of exhaust flow, in accordance with an algorithm to
estimate a quantity of ammonia consumed by chemical reactions which
are enabled by the SCR catalyst to reduce NOx into N.sub.2 and
H.sub.2O.
[0008] Another general aspect of the disclosed subject matter
relates to a method for estimating a quantity of ammonia consumed
by chemical reactions which are enabled by an SCR catalyst within
an exhaust system of an internal combustion engine to reduce NOx in
exhaust passing through the exhaust system to N.sub.2 and H.sub.2O.
The method comprises processing certain data, including data
indicative of a quantity of NOx in exhaust upstream of where
ammonia is being introduced into the exhaust system, data
indicative of a quantity of NOx in exhaust downstream of the SCR
catalyst, and data indicative of exhaust flow, in accordance with
an algorithm to estimate a quantity of ammonia consumed by chemical
reactions which are enabled by the SCR catalyst within the exhaust
system.
[0009] Another general aspect of the disclosed subject matter
relates to a system for estimating a quantity of ammonia consumed
by selective catalytic reduction (SCR) for NOx reduction in exhaust
flow through an exhaust after-treatment system. The system
comprises an SCR catalyst, an ammonia supply, an ammonia outlet
through which ammonia from the ammonia supply is introduced into
the exhaust flow, a downstream NOx sensor providing data indicative
of a quantity of NOx in exhaust flow downstream of the SCR
catalyst, a data source providing data indicative of a quantity of
NOx in exhaust flow upstream of the ammonia outlet, and a processor
for processing data from the downstream NOx sensor, data from the
data source, and data indicative of exhaust flow, in accordance
with an algorithm to estimate a quantity of ammonia consumed to
reduce NOx to N.sub.2 and H.sub.2O by chemical reactions enabled by
the SCR catalyst.
[0010] The foregoing summary is accompanied by further detail of
the disclosure presented in the Detailed Description below with
reference to the following drawings which are part of the
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is a general schematic diagram of an internal
combustion engine which utilizes SCR to reduce NOx in engine
exhaust by chemical reaction with ammonia introduced into the
exhaust.
[0012] FIG. 2 is a diagram illustrating detail of a NOx reduction
system present in FIG. 1.
[0013] FIG. 3 is a diagram of an algorithm for estimating a
quantity of reductant (NH.sub.3) consumed by chemical reaction with
NOx in the NOx reduction system of FIG. 2.
DETAILED DESCRIPTION
[0014] FIG. 1 shows a representative internal combustion engine 10
which can be used in stationary or mobile applications. For
example, engine 10 may be a diesel engine which comprises structure
forming a number of engine cylinders 12 into which fuel is injected
by fuel injectors 14 to combust with air which has entered
combustion chamber spaces of engine cylinders 12 through an intake
system 16 when cylinder intake valves 18 for controlling admission
of air from an intake manifold 20 into respective engine cylinders
12 are open. Other components which may be present in intake
systems of contemporary diesel engines, such as a turbocharger
compressor and charge air cooler, are not shown.
[0015] Engine 10 also comprises an exhaust system 22 through which
engine exhaust created by combustion of injected fuel in the
combustion chamber spaces to operate engine 10 is conveyed to
atmosphere. Cylinder exhaust valves 24 control admission of exhaust
from respective engine cylinders 12 into an exhaust manifold 26 for
further conveyance through exhaust system 22.
[0016] Exhaust system 22 includes an exhaust after-treatment system
28 for treating exhaust prior to entry into the atmosphere. Other
components which may be present in exhaust systems of contemporary
diesel engines, such as a turbocharger turbine, are not shown.
[0017] A processor-based engine control module (ECM) 30 controls
various aspects of engine operation, such as fueling of engine
cylinders 12 by fuel injectors 14. Control is accomplished by
processing various input data, indicated generally by reference
numeral 32, to develop control data for control of functions being
performed by various devices.
[0018] Exhaust after-treatment system 28 is shown in detail in FIG.
2 to comprise structure through which exhaust is constrained to
pass. The particular structure shown comprises a generally
cylindrical housing 34 having an axial length, an exhaust entrance
36 at an upstream axial end, and an exhaust exit 38 at a downstream
axial end. Arrows 40 indicate a direction of exhaust flow into,
through, and out of interior space of housing 34.
[0019] Within its interior space, housing 34 contains a diesel
oxidation catalyst (DOC) 42 downstream of exhaust entrance 36 and
an SCR catalyst 44 downstream of DOC 42. Exhaust which enters the
interior space of housing 34 through exhaust entrance 36 is forced
to pass first through DOC 42 and subsequently through SCR catalyst
44 before exiting through exhaust exit 38. DOC 42 treats engine
exhaust by removing certain entrained matter, such as the soluble
organic fraction of diesel particulate matter. SCR catalyst 44
treats engine exhaust by reducing NOx according to chemical
reactions such as:
4NO+4NH3+O2.fwdarw.4N2+6H2O
NO+NO2+2NH3.fwdarw.2N2+3H2O
6NO2+8NH3.fwdarw.7N2+12H2O
[0020] SCR catalyst 44 may be a type which not only reduces NOx but
also traps entrained particulate matter (soot) and therefore
requires occasional regeneration.
[0021] An ammonia supply 46 stores ammonia which is used for NOx
reduction Ammonia from supply 46 is introduced into the interior of
housing 34 through a conduit 48 having an outlet 50 disposed at a
location downstream of DOC 42 and upstream of SCR catalyst 44. FIG.
2 is intended to portray good distribution of ammonia within the
exhaust flow without reference to specific structural details of
how that is accomplished so that a continuing presence of ammonia
can be assured over as large a surface area of SCR catalyst 44 as
possible.
[0022] A processor-based ammonia dosing controller 52 controls the
introduction of ammonia from ammonia supply 46 into housing 34 by
processing various data, including data from ECM 30 with which it
has communication. Controller 52 also processes data according to
an algorithm for estimating a quantity of ammonia consumed by
conversion of NOx in exhaust passing through exhaust system 22.
That algorithm 54 will be explained with reference to FIG. 3.
[0023] The algorithm processes data indicating a quantity of NOx as
measured at a location upstream of outlet 50 and data indicating a
quantity of NOx as measured at a location downstream of SCR
catalyst 44. These data are provided respectively by an upstream
NOx sensor 56 upstream of DOC 42 and a downstream NOx sensor 58,
both shown in FIG. 2. NOx sensor 58 is a type which also senses
ammonia, and so the algorithm is premised on the assumption that
ammonia is injected in quantity which causes minimal, nor no, slip.
NOx sensor 56 may be replaced by a sufficiently accurate virtual
NOx sensor. NOx sensor 56 may alternately be placed downstream of
DOC 42 but upstream of ammonia outlet 50.
[0024] Controller 52 processes data from NOx sensor 56 indicating a
quantity of NOx in untreated, i.e. "engine out", exhaust and data
from NOx sensor 58 indicating a quantity of NOx in exhaust which
has been treated by SCR using ammonia stored on the surface of SCR
44. The processing performs a first calculation 60 which yields a
fraction equal to the quantity of NOx indicated by downstream NOx
sensor 58 divided by the quantity of NOx indicated by upstream NOx
sensor 56. A second calculation 62 subtracts the calculated
fraction from unity, leaving a resulting fraction representing the
fraction of NOx which has been reduced.
[0025] Using the three chemical reactions given above and the
result of calculation 62, algorithm 54 performs a calculation 64 of
a quantity of ammonia which would have been consumed in order to
reduce NOx to the resulting fraction calculated by step 62. Because
the NOx sensors do not distinguish between NO and NO.sub.2, the
calculation may utilize a look-up table containing relative
proportions of NO and NO.sub.2 in the exhaust as a function of
engine operation obtained by known techniques. The look-up table
has been derived from previous mapping of engine exhaust at various
engine operating conditions during engine development. Hence,
algorithm 54 is repeatedly calculating the quantity of ammonia
consumed to reduce NO and the quantity of ammonia consumed to
reduce NO.sub.2 over each interval of time between successive
calculations as engine 10 operates. The calculation of the total
quantity of ammonia consumed from an initial time to a present time
is obtained by adding the respective quantities consumed to reduce
NO and NO.sub.2 during each interval between calculations. Because
the calculation prior to a calculation 66 is based in parts per
million (ppm), it must be converted from ppm to a flow rate
[mass/time]. An estimate of the actual consumption is therefore
calculated by calculation 66 which multiplies the result of
calculation 64 by exhaust flow as measured or estimated in any
suitably appropriate way. Depending on the unit of measurement of
exhaust flow, a calculation 68 may be needed to convert the result
of calculation 66 to desired units of ammonia consumption.
* * * * *