U.S. patent application number 14/057237 was filed with the patent office on 2015-04-23 for gasoline dithering for spark-ignited gaseous fuel internal combustion engine.
The applicant listed for this patent is Cummins IP, Inc.. Invention is credited to Joseph P. McIntier, Tamas Szailer.
Application Number | 20150107226 14/057237 |
Document ID | / |
Family ID | 52824947 |
Filed Date | 2015-04-23 |
United States Patent
Application |
20150107226 |
Kind Code |
A1 |
Szailer; Tamas ; et
al. |
April 23, 2015 |
GASOLINE DITHERING FOR SPARK-IGNITED GASEOUS FUEL INTERNAL
COMBUSTION ENGINE
Abstract
An internal combustion engine system of the present application
includes a spark-ignited internal combustion engine that is powered
by a gaseous fuel. The engine system also includes an exhaust
system that is in exhaust gas receiving communication with the
internal combustion engine. The exhaust system includes an exhaust
treatment component. Additionally, the exhaust system includes a
liquid fuel injection system in liquid fuel injecting communication
with the exhaust system to inject liquid fuel into exhaust gas
upstream of the exhaust treatment component.
Inventors: |
Szailer; Tamas; (Seymour,
IN) ; McIntier; Joseph P.; (Columbus, IN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cummins IP, Inc. |
Columbus |
IN |
US |
|
|
Family ID: |
52824947 |
Appl. No.: |
14/057237 |
Filed: |
October 18, 2013 |
Current U.S.
Class: |
60/274 ;
60/295 |
Current CPC
Class: |
F01N 3/206 20130101;
F02D 19/0642 20130101; Y02T 10/30 20130101; F01N 2900/1624
20130101; F01N 3/2066 20130101; Y02T 10/40 20130101; Y02T 10/47
20130101; F01N 2560/025 20130101; Y02T 10/36 20130101; F01N 2610/03
20130101; Y02T 10/22 20130101; F01N 2900/1602 20130101; Y02T 10/12
20130101; F01N 9/005 20130101; F01N 3/103 20130101; F01N 3/101
20130101 |
Class at
Publication: |
60/274 ;
60/295 |
International
Class: |
F01N 3/20 20060101
F01N003/20 |
Claims
1. An internal combustion engine system, comprising: a
spark-ignited internal combustion engine powered by a gaseous fuel;
an exhaust system in exhaust gas receiving communication with the
internal combustion engine, the exhaust system comprising an
exhaust treatment component; and a liquid fuel injection system in
liquid fuel injecting communication with the exhaust system to
inject liquid fuel into exhaust gas upstream of the exhaust
treatment component.
2. The internal combustion engine system of claim 1, wherein the
gaseous fuel comprises natural gas.
3. The internal combustion engine system of claim 1, wherein the
liquid fuel comprises gasoline.
4. The internal combustion engine system of claim 1, wherein the
liquid fuel injection system injects liquid fuel into the exhaust
gas based on an air-to-fuel ratio of the exhaust gas generated by
the spark-ignited internal combustion engine.
5. The internal combustion engine system of claim 1, wherein the
spark-ignited internal combustion engine generates exhaust gas with
an air-to-fuel ratio above 1.0.
6. The internal combustion engine system of claim 1, wherein the
exhaust treatment component stores oxygen, and wherein the liquid
fuel injection system injects liquid fuel into the exhaust gas
based on an oxygen storage capacity of the exhaust treatment
component.
7. The internal combustion engine system of claim 1, wherein the
liquid fuel injection system injects liquid fuel into the exhaust
gas during a cold start of the spark-ignited internal combustion
engine.
8. The internal combustion engine system of claim 1, wherein the
exhaust system comprises an exhaust manifold coupled to the
spark-ignited internal combustion engine, and wherein the liquid
fuel injection system injects liquid fuel into the exhaust
manifold.
9. The internal combustion engine system of claim 1, further
comprising a gaseous fuel injection system in gaseous fuel
injecting communication with the spark-ignited internal combustion
engine, wherein the liquid fuel injection system injects liquid
fuel into the exhaust gas independently of the injection of gaseous
fuel injected into the engine by the gaseous fuel injection
system.
10. The internal combustion engine system of claim 1, wherein
quantity and timing of the injection of liquid fuel into the
exhaust gas by the liquid fuel injection system is based solely on
conditions of the internal combustion engine system downstream of
the spark-ignited internal combustion engine.
11. The internal combustion engine system of claim 1, wherein the
exhaust treatment component comprises an oxidation catalyst.
12. The internal combustion engine system of claim 1, wherein the
exhaust treatment component comprises a three-way catalyst.
13. The internal combustion engine system of claim 1, wherein the
liquid fuel injection system comprises a retrofitted diesel exhaust
fluid injection system.
14. The internal combustion engine system of claim 1, wherein the
exhaust treatment component comprises a nitrogen oxide reduction
catalyst.
15. The internal combustion engine system of claim 1, wherein the
gaseous fuel comprises substantially solely natural gas.
16. An electronic control module for a spark-ignited internal
combustion engine powered by a gaseous fuel, comprising: an exhaust
system condition module that determines a condition of an exhaust
system in exhaust gas receiving communication with the
spark-ignited internal combustion engine; and a liquid fuel control
module that commands the dithering of a liquid fuel into the
exhaust system based on the condition of the exhaust system.
17. The electronic control module of claim 16, wherein the exhaust
system comprises an oxidation catalyst, and wherein the condition
of the exhaust system comprises an oxygen storage capacity of the
oxidation catalyst.
18. The electronic control module of claim 16, wherein the
condition of the exhaust system comprises an air-to-fuel ratio of
exhaust gas generated by the spark-ignited internal combustion
engine.
19. The electronic control module of claim 16, wherein the
condition of the exhaust system comprises an exhaust gas
temperature below a minimum threshold.
20. A method for dithering a liquid fuel into an exhaust system in
exhaust receiving communication with a spark-ignited internal
combustion engine powered by a gaseous fuel, the method comprising:
determining a condition of the exhaust system; and injecting a
liquid fuel into exhaust gas flowing through the exhaust system
based on the condition of the exhaust system.
Description
FIELD
[0001] This disclosure relates to spark-ignited gaseous fuel
internal combustion engines, and more particularly to an exhaust
system that dithers an liquid fuel for such internal combustion
engines.
BACKGROUND
[0002] Emissions regulations for internal combustion engines have
become more stringent over recent years. Environmental concerns
have motivated the implementation of stricter emission requirements
for internal combustion engines throughout much of the world.
Governmental agencies, such as the Environmental Protection Agency
(EPA) in the United States, carefully monitor the emission quality
of engines and set acceptable emission standards, to which all
engines must comply. Generally, emission requirements vary
according to engine type. Emission tests for spark-ignited gasoline
(e.g., aqueous or non-gaseous fuel) engines typically monitor the
release of carbon monoxide, nitrogen oxides (NOx), and unburned
hydrocarbons (UHC). Catalytic converters (e.g., oxidation
catalysts) implemented in an exhaust gas aftertreatment system have
been used to eliminate many of the regulated pollutants present in
exhaust gas generated from gasoline powered engines. For example,
some known three-way catalysts include carefully selected catalytic
material formulations to specifically oxidize carbon monoxide and
unburned hydrocarbons, and reduce nitrogen oxides to less harmful
components, present in the exhaust gas. Conventional three-way
catalysts are designed to oxidize or reduce such pollutants more
efficiently for engines running above the stoichiometric
air-to-fuel ratio (i.e., rich conditions).
[0003] Recently, due at least in part to high crude oil prices,
environmental concerns, and future fuel availability, many internal
combustion engine designers have looked to at least partially
replace crude oil fossil fuels, e.g., gasoline and diesel, with
so-called alternative fuels for powering internal combustions
engines. Desirably, by replacing or reducing the use of fossil
fuels with alternative fuels, the cost of fueling internal
combustion engines is decreased, harmful environmental pollutants
are decreased, and/or the future availability of fuels is
increased. Known alternative fuels include gaseous fuels or fuels
with gaseous hydrocarbons, such as, for example, natural gas,
petroleum gas (propane), and hydrogen. The combustion byproducts
present in exhaust gas generated by spark-ignited gaseous-powered
engines are similar to those present in exhaust gas generated by
spark-ignited non-gaseous-powered engines. Accordingly,
conventional gaseous-powered engine systems utilize the same or
similar oxidation catalysts found in non-gaseous-powered engine
systems to oxidize the regulated pollutants generated by
gaseous-powered engines.
[0004] Traditionally, gaseous-powered engines are operated at rich
air-to-fuel ratios (e.g., richer than stoichiometric) in order to
reduce oxygen concentrations within the exhaust gas, and thus the
formation of carbon monoxide and nitrogen oxides. However, lower
oxygen concentrations in the exhaust gas may fail to adequately
replenish oxidation catalysts configured to store oxygen for NOx
reduction purposes.
[0005] Additionally, operating a gaseous-powered engine under
stoichiometric or richer air-to-fuel ratios results in a relatively
low brake thermal efficiency of the engine. Operating at such
air-to-fuel ratios causes high combustion temperatures, which
result in high component temperatures in the engine, and the
necessity to reduce output power to avoid component failure.
However, in view of the premium placed on satisfying exhaust
emissions regulations, conventional gaseous-powered engines are
designed to meet exhaust emissions regulations at the expense of
thermal efficiency and power density.
[0006] Finally, many internal combustion engine systems experience
long delays between a cold start of the engine and the exhaust gas
reaching temperatures necessary for efficient reduction of NOx in
the exhaust gas.
SUMMARY
[0007] The subject matter of the present application has been
developed in response to the present state of the art, and in
particular, in response to the problems and needs in the art that
have not yet been fully solved by currently available exhaust
systems for gaseous-powered internal combustion engines.
Accordingly, the subject matter of the present application has been
developed to provide an exhaust system for a gaseous-powered engine
that overcomes at least some shortcomings of prior art systems. For
example, in some embodiments described herein, an exhaust system
for a gaseous-powered engine dithers an aqueous or liquid fuel,
such as gasoline, into the exhaust system for NOx reduction
purposes to allow the engine to run leaner (e.g., with a higher
air-to-fuel ratio, such as greater than 1.0) compared to
conventional systems, which results in an increase in the thermal
efficiency and power density of the engine. Additionally, in
certain embodiments described herein, the dithering of liquid fuel
into the exhaust system promotes a faster increase in exhaust gas
temperature after a cold start than conventional systems.
[0008] According to some embodiments, an internal combustion engine
system of the present application includes a spark-ignited internal
combustion engine that is powered by a gaseous fuel. The engine
system also includes an exhaust system that is in exhaust gas
receiving communication with the internal combustion engine. The
exhaust system includes an exhaust treatment component.
Additionally, the exhaust system includes a liquid fuel injection
system in liquid fuel injecting communication with the exhaust
system to inject liquid fuel into exhaust gas upstream of the
exhaust treatment component.
[0009] In certain implementations of the internal combustion engine
system, the gaseous fuel is natural gas. In yet some
implementations, the liquid fuel is gasoline.
[0010] According to some implementations of the internal combustion
engine system, the liquid fuel injection system injects liquid fuel
into the exhaust gas based on an air-to-fuel ratio of the exhaust
gas generated by the spark-ignited internal combustion engine. The
spark-ignited internal combustion engine may generate exhaust gas
with an air-to-fuel ratio above 1.0.
[0011] In some implementations, the exhaust treatment component
stores oxygen, and the liquid fuel injection system injects liquid
fuel into the exhaust gas based on an oxygen storage capacity of
the exhaust treatment component. Alternatively, or additionally,
the liquid fuel injection system injects liquid fuel into the
exhaust gas during a cold start of the spark-ignited internal
combustion engine.
[0012] The exhaust system of the internal combustion engine, in
some implementations, includes an exhaust manifold that is coupled
to the spark-ignited internal combustion engine. The liquid fuel
injection system can inject the liquid fuel into the exhaust
manifold.
[0013] According to certain implementations, the engine system also
includes a gaseous fuel injection system that is in gaseous fuel
injecting communication with the spark-ignited internal combustion
engine. The liquid fuel injection system can be configured to
inject liquid fuel into the exhaust gas independently of the
injection of gaseous fuel injected into the engine by the gaseous
fuel injection system. The quantity and timing of the injection of
liquid fuel into the exhaust gas by the liquid fuel injection
system may be based solely on conditions of the internal combustion
engine system downstream of the spark-ignited internal combustion
engine.
[0014] The exhaust treatment component is an oxidation catalyst in
some implementations, a three-way catalyst in some implementations,
and a nitrogen oxide reduction catalyst in yet some
implementations. The liquid fuel injection system is a retrofitted
diesel exhaust fluid injection system in some certain
implementations. The gaseous fuel can be substantially solely
natural gas.
[0015] According to another embodiment, an electronic control
module for a spark-ignited internal combustion engine powered by a
gaseous fuel includes an exhaust system condition module that
determines a condition of an exhaust system in exhaust gas
receiving communication with the spark-ignited internal combustion
engine. The electronic control module can also include a liquid
fuel control module that commands the dithering of a liquid fuel
into the exhaust system based on the condition of the exhaust
system.
[0016] In some implementations of the electronic control modules,
the exhaust system includes an oxidation catalyst, and the
condition of the exhaust system includes an oxygen storage capacity
of the oxidation catalyst. The condition of the exhaust system can
be an air-to-fuel ratio of exhaust gas generated by the
spark-ignited internal combustion engine in certain
implementations. The condition of the exhaust system can be an
exhaust gas temperature below a minimum threshold in yet some
implementations.
[0017] According to yet another embodiment, a method for dithering
a liquid fuel into an exhaust system in exhaust receiving
communication with a spark-ignited internal combustion engine
powered by a gaseous fuel is disclosed. The method includes
determining a condition of the exhaust system, and injecting a
liquid fuel into exhaust gas flowing through the exhaust system
based on the condition of the exhaust system.
[0018] The described features, structures, advantages, and/or
characteristics of the subject matter of the present disclosure may
be combined in any suitable manner in one or more embodiments
and/or implementations. In the following description, numerous
specific details are provided to impart a thorough understanding of
embodiments of the subject matter of the present disclosure. One
skilled in the relevant art will recognize that the subject matter
of the present disclosure may be practiced without one or more of
the specific features, details, components, materials, and/or
methods of a particular embodiment or implementation. In other
instances, additional features and advantages may be recognized in
certain embodiments and/or implementations that may not be present
in all embodiments or implementations. Further, in some instances,
well-known structures, materials, or operations are not shown or
described in detail to avoid obscuring aspects of the subject
matter of the present disclosure. The features and advantages of
the subject matter of the present disclosure will become more fully
apparent from the following description and appended claims, or may
be learned by the practice of the subject matter as set forth
hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order that the advantages of the subject matter may be
more readily understood, a more particular description of the
subject matter briefly described above will be rendered by
reference to specific embodiments that are illustrated in the
appended drawings. Understanding that these drawings depict only
typical embodiments of the subject matter and are not therefore to
be considered to be limiting of its scope, the subject matter will
be described and explained with additional specificity and detail
through the use of the drawings, in which:
[0020] FIG. 1 is a schematic diagram of an internal combustion
engine system having an exhaust system that dithers a liquid fuel
according to one embodiment;
[0021] FIG. 2 is a schematic diagram of an electronic control
module of an internal combustion engine system;
[0022] FIG. 3 is a schematic diagram of an internal combustion
engine system having an exhaust system with a three-way catalyst
and a gasoline injector that dithers gasoline into the exhaust
system according to another embodiment; and
[0023] FIG. 4 is a schematic flow chart diagram of a method for
retrofitting an existing exhaust system if necessary and dithering
a liquid fuel into the exhaust system according to one
embodiment.
DETAILED DESCRIPTION
[0024] Reference throughout this specification to "one embodiment,"
"an embodiment," or similar language means that a particular
feature, structure, or characteristic described in connection with
the embodiment is included in at least one embodiment of the
subject matter of the present disclosure. Appearances of the
phrases "in one embodiment," "in an embodiment," and similar
language throughout this specification may, but do not necessarily,
all refer to the same embodiment. Similarly, the use of the term
"implementation" means an implementation having a particular
feature, structure, or characteristic described in connection with
one or more embodiments of the subject matter of the present
disclosure, however, absent an express correlation to indicate
otherwise, an implementation may be associated with one or more
embodiments.
[0025] According to one general embodiment of an internal
combustion engine system 100 shown in FIG. 1, the system includes
an internal combustion engine 110 coupled to an exhaust system 120.
The engine 110 is a spark-ignited engine fueled by gaseous
hydrocarbons or fuel 140, such as natural gas, petroleum gas
(propane), and hydrogen. As defined herein, gaseous fuels, as
opposed to non-gaseous liquid or aqueous fuels (e.g., gasoline and
diesel), are those that are introduced and managed within the
engine in a gaseous state, as opposed to, a liquid state. In
specific implementations, the engine 110 is a spark-ignited engine
fueled by natural gas. Spark-ignited gaseous fuel engines are
configured and calibrated differently than spark-ignited
non-gaseous fuel engines. Gaseous fuel engines introduce
considerations not present with non-gaseous engines. For example,
non-gaseous engines do not produce significant amounts of certain
combustion byproducts produced by gaseous engines. Of particular
relevance to the illustrated embodiments of the system 100 of the
present disclosure, non-gaseous fuel engines produce no more than
nominal amounts of methane compared to gaseous fuel engines, which
produce large amounts of methane when the gaseous fuel itself
contains a large amount of methane, which is normal with natural
gas and a wide variety of other gaseous fuels.
[0026] The internal combustion engine system 100 also includes an
air intake system that receives and directs air into the engine
110. Accordingly, the air intake system includes an air inlet that
is at essentially atmospheric pressure, thus enabling fresh air to
enter the air system. In one embodiment, prior to the fresh air
entering the engine 110, it receives a metered amount of gaseous
fuel 140. The quantity and timing of the gaseous fuel 140 added to
the air is controlled by an electronic control module 130 based on
any of various operating conditions of the engine 100, such as
engine speed, torque demand, air temperature and pressure, exhaust
temperature and pressure, and the like. The gaseous fuel 140 can be
stored in a storage tank and injected into the fresh air via a fuel
injector and fuel pump specifically configured to dose a gaseous
material. Although not shown, the fresh air may also be mixed with
recirculated exhaust gas from an exhaust gas recirculation (EGR)
line. The fuel and air mixture may enter a compressor of a
turbocharger before entering the engine. Alternatively, the gaseous
fuel 140 can be added to the air after the compressor. For example,
in one implementation, the gaseous fuel 140 is directly injected
into the combustion chambers of the engine via a common rail and a
plurality of fuel injectors. Whether the fuel is injected directly
into the combustion chambers or injected into the air upstream of
the engine, the combined fuel and air mixture is ignited, and the
fuel is combusted, via a spark-ignition system to generate a
pressure differential within the chambers for powering the
engine.
[0027] Combustion of the gaseous fuel in the engine 110 produces
exhaust gas that is operatively vented to the exhaust system 120
after driving a turbine of a turbocharger in some implementations.
Generally, the exhaust system 120 treats, regulates, and directs
the exhaust gas received from the engine. The exhaust system 120
can include one or more exhaust treatment components, such as, for
example, three-way catalysts, oxidation catalysts, filters,
adsorbers, and the like, for treating (i.e., removing pollutants
from) the exhaust gas. Additionally, the exhaust system 120 can
include exhaust flow regulation devices to regulate the exhaust gas
flow rate and pressure (e.g., backpressure) of exhaust gas flowing
into, through, and out of the system 120. Also, the exhaust system
120 can include actuators and valves to direct exhaust gas to one
or more destinations. For example, the exhaust system 120 can
include an EGR valve that is actuatable to direct (e.g., vent) a
portion of the received exhaust gas into the atmosphere as expelled
exhaust and direct a portion of the received exhaust gas into one
or more EGR lines for recirculation back into the combustion
chambers.
[0028] The internal combustion engine system 100 also includes a
sub-system for dithering liquid fuel 150 into the exhaust gas
generated by the engine 110 before the exhaust gas passes through
the exhaust system 120. Although not shown, the liquid fuel 150 can
stored in a storage tank and injected into the exhaust gas via a
fuel injector and fuel pump specifically configured to dose a
liquid material. Generally, liquid material injectors and pumps are
able to more precisely, accurately, and responsively administer
doses of liquid material than gaseous material injectors and pumps.
Moreover, liquid fuels, such as gasoline, have a lower light-off
temperature than gaseous fuels, such as natural gas. Accordingly,
the liquid fuel added to the exhaust gas lowers the temperature at
which the oxidation of the exhaust gas occurs, which leads to
improved thermal management of the exhaust system.
[0029] As shown in FIG. 1, in certain embodiments, the liquid fuel
150 is injected into the exhaust gas upstream of the exhaust system
120. In other words, in certain embodiments, the liquid fuel 150 is
configured to be injected into the exhaust gas upstream of the
exhaust treatment components of the exhaust system 120. The liquid
fuel 150 can be injected into the exhaust gas upstream of all
exhaust treatment components, or downstream of some components and
upstream of others. Generally, the liquid fuel 150 is injected
upstream of the component or components that utilize excess
hydrocarbons in the exhaust gas to effectuate desired results. For
example, the excess hydrocarbons generated by the injected liquid
fuel 150 can be utilized by an oxidation catalyst to increase
exhaust gas temperature or a three-way catalyst to increase the NOx
reduction efficiency of the exhaust system 120.
[0030] The quantity and timing of the liquid fuel 150 dithered into
the exhaust gas is controlled by the electronic control module 130
based on any of various operating conditions of the engine 100,
such as exhaust flow rate, exhaust temperature and pressure,
exhaust air-to-fuel ratio, exhaust system operating conditions
(e.g., NOx conversion capacity, oxygen storage capacity, and age of
the system), and the like. In some implementations, the electronic
control module 130 controls the injection of the gaseous fuel 140
into the engine independently of the injection of the liquid fuel
150 into the exhaust system 120. In other words, the quantity and
timing of the injection of liquid fuel 150 is not dependent on the
quantity and timing of the injection of the gaseous fuel 140.
Generally, the electronic control module 130 communicates with
and/or receives communication from various components of the system
100 via electronic signals (as indicated by dashed lines). The
electronic control module 130 controls the operation of the engine
system 100 and associated sub-systems, such as the engine 110 and
exhaust system 120. The electronic control module 130 is depicted
in FIG. 1 as a single physical unit, but can include two or more
physically separated units or components in some embodiments if
desired. In certain embodiments, the electronic control module 130
receives multiple inputs, processes the inputs, and transmits
multiple outputs. The multiple inputs may include sensed and/or
calculated measurements from the sensors and various user inputs.
The inputs are processed by the electronic control module 130 using
various algorithms, stored data, and other inputs to update the
stored data and/or generate output values. The generated output
values and/or commands are transmitted to other components of the
controller and/or to one or more elements of the engine system 10
to control the system to achieve desired results.
[0031] According to a specific embodiment, and referring to FIG. 2,
the electronic control module 130 includes an exhaust system
condition module 160 and a liquid fuel control module 164.
Generally, the exhaust system condition module 160 and liquid fuel
control module 164 cooperate to generate a liquid fuel dosing
command 168 based on sensor inputs 166. The sensor inputs 166 may
include measured or calculated conditions of the engine system 100
as discussed above. For example, in one implementation, the sensor
inputs 166 include at least one of an air-to-fuel ratio input, a
catalyst oxygen storage input, an exhaust temperature input, and an
engine ON input. In some implementations, the sensor inputs 166
indicate only conditions of the engine system downstream of the
engine 110 (e.g., solely based on conditions of the exhaust system
120). Based on the sensor inputs 166, the exhaust system condition
module 160 determines an exhaust system condition 162 of the
exhaust system 120. Generally, the exhaust system condition 162
represents a condition of the exhaust system affected by the
presence of unburned hydrocarbons in the exhaust gas. In one
implementation, the exhaust system condition 162 can be the exhaust
gas temperature and/or the NOx reduction efficiency of the exhaust
system 120. Based on the exhaust system condition 162, the liquid
fuel control module 164 determines the quantity of liquid fuel
necessary to achieve a desired result, and issues the liquid fuel
dosing command 168, which commands the engine system 100 to inject
the determined quantity of liquid fuel into the exhaust gas at an
appropriate time to realize the desired result.
[0032] In one implementation, the input includes one of an engine
ON input indicating the initiation of a cold start of the engine
110 and the exhaust system condition 162 is the exhaust gas
temperature. Alternatively, the input includes a measurement from
an exhaust temperature sensor. The liquid fuel control module 164
compares the exhaust gas temperature received from the exhaust
system condition module 160 to a corresponding predetermined
threshold. If the exhaust gas temperature is below the threshold,
the liquid fuel control module 164 determines a quantity of liquid
fuel necessary to reach the exhaust gas temperature threshold, and
issues a liquid fuel dosing command 168 corresponding with the
determined quantity.
[0033] In another implementation, the input includes an air-to-fuel
ratio input and a catalyst oxygen storage input, and the exhaust
system condition 162 is the NOx reduction efficiency or performance
of the exhaust system 120. The air-to-fuel ratio input can be
determined based on an estimation of the amount of oxygen and fuel
in the exhaust gas based on known operating conditions of the
engine. The catalyst oxygen storage input indicates the quantity of
oxygen stored on an catalyst (e.g., three-way catalyst) of the
exhaust system 120, or the capacity of the catalyst to store
oxygen. The liquid fuel control module 164 compares the NOx
reduction efficiency of the exhaust system 120 received from the
exhaust system condition module 160 to a corresponding
predetermined threshold. If the NOx reduction efficiency is below
the threshold, the liquid fuel control module 164 determines a
quantity of liquid fuel necessary to reach the NOx reduction
efficiency threshold, and issues a liquid fuel dosing command 168
corresponding with the determined quantity.
[0034] Referring to FIG. 3, a specific embodiment of an internal
combustion engine system 200 is shown. The engine system 200 is
similar to the engine system 100 of FIG. 1, with like numbers and
titles referring to like features. Accordingly, unless otherwise
indicated, the description of the features of the engine system 100
applies equally to the corresponding features of the engine system
200. Like the engine system 100, the engine system 200 includes a
gaseous fuel internal combustion engine 210 and an electronic
control module 230. The engine 210 is a spark-ignited engine fueled
by natural gas supplied from a natural gas tank 240. The natural
gas from the tank 240 is supplied to the engine 210 via a natural
gas injector 242 that is controlled by the electronic control
module 130. The natural gas is injected into the air before or
after the air enters the engine 210. The combusted natural gas
produces exhaust gas that is received by an exhaust manifold 212 in
exhaust receiving communication with the engine 210. The engine 210
is in exhaust providing communication with an exhaust system that
includes a three-way catalyst 220.
[0035] The three-way catalyst 220 can be a flow-through type
catalyst having a catalyst bed exposed to the exhaust gas flowing
through a main exhaust line of the exhaust system and past the bed.
The catalyst bed includes a catalytic layer disposed on a washcoat
or carrier layer. The carrier layer can include any of various
materials (e.g., oxides) capable of suspending the catalytic layer
therein. The catalyst layer is made from one or more catalytic
materials selected to react with (e.g., oxidize) one or more
pollutants in the exhaust gas. The catalytic materials of the
three-way catalyst 220 can include any of various materials, such
as precious metals platinum, palladium, and rhodium, as well as
other materials, such as transition metals cerium, iron, manganese,
and nickel. Further, the catalyst materials can have any of various
ratios relative to each other for oxidizing and reducing relative
amounts and types of pollutants as desired.
[0036] Generally, the three-way catalyst 220 is so termed because
it contains catalytic materials specifically selected to react with
and oxidize or reduce three specific pollutants. The three specific
pollutants include carbon monoxide (CO), unburned hydrocarbons
(UHC), and nitrogen oxides (NOx). In some implementations, the
three-way catalyst 220 is housed within the same housing, and the
catalyst includes three catalyst beds positioned adjacent each
other to form three separate catalyst stages. Although the
three-way catalyst 220 is depicted as a single unit in FIG. 3, in
some embodiments, the three-way catalyst can be formed of two or
more separate, disparate units. For example, in one embodiment, the
three-way catalyst 220 is housed within a single housing, while in
another embodiment, the three-way catalyst 220 includes three
separate catalysts (e.g., a CO oxidation catalyst, a methane
oxidation catalyst, and a NOx reduction catalyst) each housed
within a separate housing. In one embodiment, the NOx catalyst of
the three-way catalyst 220 is a NOx adsorber catalyst. In another
embodiment, the NOx catalyst of the three-way catalyst 220 is a
selective catalytic reduction (SCR) catalyst that forms part of a
SCR system. Although not shown, the main exhaust line of the
exhaust system may include other exhaust treatment devices, such as
filters, that further treat the exhaust gas before it vents into
the atmosphere.
[0037] Like the engine system 100, the engine system 200 includes a
sub-system for dithering gasoline into the exhaust gas generated by
the engine 210 before the exhaust gas enters the three-way catalyst
220. The gasoline is stored in a gasoline tank 250 and injected
into the exhaust gas via a gasoline injector 252, which can receive
gasoline from the tank via a fuel pump 254 operatively coupled with
the engine 210. In the illustrated embodiment of FIG. 3, the
gasoline injector 252 is positioned such that gasoline is injected
into the exhaust gas located within the exhaust manifold 212.
Alternatively, the gasoline injector 252 can be positioned
downstream of the exhaust manifold 212 to inject gasoline into the
exhaust gas downstream of the exhaust manifold. The quantity and
timing of the gasoline dithered into the exhaust gas is controlled
by an electronic control module 230 Like the electronic control
module 130, the electronic control module 230 is configured to
dither gasoline directly into the exhaust gas on an as-needed basis
to promote exhaust gas conditions conducive to achieving desired
exhaust system performance.
[0038] According to certain implementations associated with an
existing internal combustion engine that has an exhaust system
equipped with a diesel exhaust fluid (DEF) injection system, the
components of the DEF injection system can be utilized to inject
gasoline (or other liquid fuel) instead of DEF. As mentioned above,
certain internal combustion engine systems have an exhaust
aftertreatment system with a selective catalytic reduction (SCR)
system configured to reduce NOx on an SCR catalyst in the presence
of ammonia. The ammonia is introduced into the exhaust gas stream
in the form of an aqueous reductant, such as urea, that decomposes
into ammonia after being injected into an exhaust gas stream. The
aqueous reductant is stored in a reductant storage tank. In some
implementations, each internal combustion engine system 100, 200
can be an internal combustion engine system with a DEF injection
system that has been retrofitted to inject a liquid fuel instead of
DEF. For example, the DEF injection system can be evacuated of DEF
by, among other things, emptying DEF from the DEF storage tank.
Then, the DEF storage tank can be filled with aqueous fuel. Because
DEF is in a liquid or aqueous state, the components of the DEF
injection system (e.g., storage tank, pump, injector, delivery
lines, etc.) are conducive to handling liquid or aqueous fuel.
Accordingly, a DEF injection system can be easily retrofitted to
handle and inject a liquid fuel without substantial modifications,
if any, to the structural components of the DEF injection system.
In certain implementations, the DEF injection control system,
including injection algorithms and mapping, is replaced with a
liquid fuel injection control system as part of the retrofit.
[0039] The exhaust system may include an oxygen storage capacity
(OSC) sensor 222 and an air-to-fuel ratio sensor 224 configured to
calculate and detect, respectively, the OSC of the three-way
catalyst 220 and the air-to-fuel ratio of exhaust gas entering the
three-way catalyst. The OSC sensor 222 can be a virtual sensor that
estimates the OSC of the three-way catalyst 220 based on various
sensed and/or estimated inputs. In one implementation, the OSC of
the three-way catalyst 220 is determined based on a difference
between the air-to-fuel ratio of the exhaust gas upstream and
downstream of the three-way catalyst. The determination of the OSC
by the OSC sensor 22 can be further based on the application of the
air-to-fuel ratio difference to a three-way catalyst model 228 that
models the behavior of the three-way catalyst 220. The air-to-fuel
ratio of exhaust gas downstream of the three-way catalyst can be
determined by an air-to-fuel sensor 226. The air-to-fuel sensors
224, 226 can be a physical sensor that detects the air-to-fuel
ratio of the exhaust gas. The OSC sensor 222 and air-to-fuel ratio
sensor 224 are in electronic communication with the electronic
control module 230 to supply the electronic control module with the
calculated and detected OSC of the three-way catalyst 220 and the
air-to-fuel ratio of the exhaust gas. The exhaust system condition
module of the electronic control module 230 utilizes the OSC and
air-to-fuel ratio inputs from the sensors 222, 224 to determine an
exhaust system condition as described above. The electronic control
module 230 also has a gasoline control module that utilizes the
exhaust system condition to generate a gasoline dosing command that
commands actuation of the gasoline injector 252 to inject a desired
amount of gasoline into the exhaust gas.
[0040] Referring to FIG. 4, according to one embodiment, a method
300 for dithering liquid fuel into an exhaust system of an internal
combustion engine system is shown. In certain implementations, each
of the electronic control modules 130, 230 may be configured to
execute the steps of the method 300. The method 310 starts by
determining whether an existing DEF injection system is being
retrofitted for liquid fuel injection at 310. If the determination
at 310 is answered affirmatively, then the method 300 replaces the
DEF in the DEF injection system with a liquid fuel, such as
gasoline, at 320. Should an internal combustion engine system be
equipped with a liquid fuel injection system such that the
determination at 320 is answered in the negative, or after
replacing DEF in an existing DEF injection system with liquid fuel
at 320, the method 300 proceeds to determine one or more operating
conditions of the exhaust system, as well as in some
implementations one or more operating conditions of the engine, at
330. The operating conditions of the exhaust system may include the
air-to-fuel ratio of the exhaust and/or the OSC of an oxidation
catalyst. The operating conditions of the engine may include engine
speed and cold-start conditions. Based on the operating conditions
of the exhaust system, and engine system in some implementations,
the method 300 dithers the liquid fuel into the exhaust system
(e.g., the exhaust gas upstream of exhaust treatment components of
the exhaust system) at 340. Generally, the method 300 dithers
liquid fuel into the exhaust system at 340 to facilitate more
efficient reduction of NOx in the exhaust gas and/or improve
thermal management of the exhaust gas.
[0041] Although mentioned above, the liquid fuel dithering systems,
apparatus, and methods provides one or more advantages over
conventional systems. For example, in some implementations, the
liquid fuel dithering systems, apparatus, and methods of the
present disclosure may provide one or more of the following
advantages additional advantages: (1) fewer constraints on engine
performance and tuning as liquid fuel is dithered downstream of
engine; (2) smaller oxidation catalysts as less oxygen is required
to be stored when engine is running leaner; (3) lower oxidation
catalyst cost because fewer precious metals or catalytic materials
are required; (4) reduction in methane emissions; and (5) improved
response under transient operating conditions of the engine.
[0042] As will be appreciated by one skilled in the art, aspects of
the present invention may be embodied as a system, method, and/or
computer program product. Accordingly, aspects of the present
invention may take the form of an entirely hardware embodiment, an
entirely software embodiment (including firmware, resident
software, micro-code, etc.) or an embodiment combining software and
hardware aspects that may all generally be referred to herein as a
"circuit," "module," or "system." Furthermore, aspects of the
present invention may take the form of a computer program product
embodied in one or more computer readable medium(s) having program
code embodied thereon.
[0043] Many of the functional units described in this specification
have been labeled as modules, in order to more particularly
emphasize their implementation independence. For example, a module
may be implemented as a hardware circuit comprising custom VLSI
circuits or gate arrays, off-the-shelf semiconductors such as logic
chips, transistors, or other discrete components. A module may also
be implemented in programmable hardware devices such as field
programmable gate arrays, programmable array logic, programmable
logic devices or the like.
[0044] Modules may also be implemented in software for execution by
various types of processors. An identified module of program code
may, for instance, comprise one or more physical or logical blocks
of computer instructions which may, for instance, be organized as
an object, procedure, or function. Nevertheless, the executables of
an identified module need not be physically located together, but
may comprise disparate instructions stored in different locations
which, when joined logically together, comprise the module and
achieve the stated purpose for the module.
[0045] Indeed, a module of program code may be a single
instruction, or many instructions, and may even be distributed over
several different code segments, among different programs, and
across several memory devices. Similarly, operational data may be
identified and illustrated herein within modules, and may be
embodied in any suitable form and organized within any suitable
type of data structure. The operational data may be collected as a
single data set, or may be distributed over different locations
including over different storage devices, and may exist, at least
partially, merely as electronic signals on a system or network.
Where a module or portions of a module are implemented in software,
the program code may be stored and/or propagated on in one or more
computer readable medium(s).
[0046] The computer readable medium may be a tangible computer
readable storage medium storing the program code. The computer
readable storage medium may be, for example, but not limited to, an
electronic, magnetic, optical, electromagnetic, infrared,
holographic, micromechanical, or semiconductor system, apparatus,
or device, or any suitable combination of the foregoing.
[0047] More specific examples of the computer readable storage
medium may include but are not limited to a portable computer
diskette, a hard disk, a random access memory (RAM), a read-only
memory (ROM), an erasable programmable read-only memory (EPROM or
Flash memory), a portable compact disc read-only memory (CD-ROM), a
digital versatile disc (DVD), an optical storage device, a magnetic
storage device, a holographic storage medium, a micromechanical
storage device, or any suitable combination of the foregoing. In
the context of this document, a computer readable storage medium
may be any tangible medium that can contain, and/or store program
code for use by and/or in connection with an instruction execution
system, apparatus, or device.
[0048] The computer readable medium may also be a computer readable
signal medium. A computer readable signal medium may include a
propagated data signal with program code embodied therein, for
example, in baseband or as part of a carrier wave. Such a
propagated signal may take any of a variety of forms, including,
but not limited to, electrical, electro-magnetic, magnetic,
optical, or any suitable combination thereof. A computer readable
signal medium may be any computer readable medium that is not a
computer readable storage medium and that can communicate,
propagate, or transport program code for use by or in connection
with an instruction execution system, apparatus, or device. Program
code embodied on a computer readable signal medium may be
transmitted using any appropriate medium, including but not limited
to wire-line, optical fiber, Radio Frequency (RF), or the like, or
any suitable combination of the foregoing
[0049] In one embodiment, the computer readable medium may comprise
a combination of one or more computer readable storage mediums and
one or more computer readable signal mediums. For example, program
code may be both propagated as an electro-magnetic signal through a
fiber optic cable for execution by a processor and stored on RAM
storage device for execution by the processor.
[0050] Program code for carrying out operations for aspects of the
present invention may be written in any combination of one or more
programming languages, including an object oriented programming
language such as Java, Smalltalk, C++, PHP or the like and
conventional procedural programming languages, such as the "C"
programming language or similar programming languages. The program
code may execute entirely on the user's computer, partly on the
user's computer, as a stand-alone software package, partly on the
user's computer and partly on a remote computer or entirely on the
remote computer or server. In the latter scenario, the remote
computer may be connected to the user's computer through any type
of network, including a local area network (LAN) or a wide area
network (WAN), or the connection may be made to an external
computer (for example, through the Internet using an Internet
Service Provider).
[0051] The computer program product may be shared, simultaneously
serving multiple customers in a flexible, automated fashion. The
computer program product may be standardized, requiring little
customization and scalable, providing capacity on demand in a
pay-as-you-go model.
[0052] The computer program product may be stored on a shared file
system accessible from one or more servers. The computer program
product may be executed via transactions that contain data and
server processing requests that use Central Processor Unit (CPU)
units on the accessed server. CPU units may be units of time such
as minutes, seconds, hours on the central processor of the server.
Additionally the accessed server may make requests of other servers
that require CPU units. CPU units are an example that represents
but one measurement of use. Other measurements of use include but
are not limited to network bandwidth, memory usage, storage usage,
packet transfers, complete transactions etc.
[0053] Aspects of the embodiments may be described above with
reference to schematic flowchart diagrams and/or schematic block
diagrams of methods, apparatuses, systems, and computer program
products according to embodiments of the invention. It will be
understood that each block of the schematic flowchart diagrams
and/or schematic block diagrams, and combinations of blocks in the
schematic flowchart diagrams and/or schematic block diagrams, can
be implemented by program code. The program code may be provided to
a processor of a general purpose computer, special purpose
computer, sequencer, or other programmable data processing
apparatus to produce a machine, such that the instructions, which
execute via the processor of the computer or other programmable
data processing apparatus, create means for implementing the
functions/acts specified in the schematic flowchart diagrams and/or
schematic block diagrams block or blocks.
[0054] The program code may also be stored in a computer readable
medium that can direct a computer, other programmable data
processing apparatus, or other devices to function in a particular
manner, such that the instructions stored in the computer readable
medium produce an article of manufacture including instructions
which implement the function/act specified in the schematic
flowchart diagrams and/or schematic block diagrams block or
blocks.
[0055] The program code may also be loaded onto a computer, other
programmable data processing apparatus, or other devices to cause a
series of operational steps to be performed on the computer, other
programmable apparatus or other devices to produce a computer
implemented process such that the program code which executed on
the computer or other programmable apparatus provide processes for
implementing the functions/acts specified in the flowchart and/or
block diagram block or blocks.
[0056] The schematic flowchart diagrams and/or schematic block
diagrams in the Figures illustrate the architecture, functionality,
and operation of possible implementations of apparatuses, systems,
methods and computer program products according to various
embodiments of the present invention. In this regard, each block in
the schematic flowchart diagrams and/or schematic block diagrams
may represent a module, segment, or portion of code, which
comprises one or more executable instructions of the program code
for implementing the specified logical function(s).
[0057] It should also be noted that, in some alternative
implementations, the functions noted in the block may occur out of
the order noted in the Figures. For example, two blocks shown in
succession may, in fact, be executed substantially concurrently, or
the blocks may sometimes be executed in the reverse order,
depending upon the functionality involved. Other steps and methods
may be conceived that are equivalent in function, logic, or effect
to one or more blocks, or portions thereof, of the illustrated
Figures.
[0058] Although various arrow types and line types may be employed
in the flowchart and/or block diagrams, they are understood not to
limit the scope of the corresponding embodiments. Indeed, some
arrows or other connectors may be used to indicate only the logical
flow of the depicted embodiment. For instance, an arrow may
indicate a waiting or monitoring period of unspecified duration
between enumerated steps of the depicted embodiment. It will also
be noted that each block of the block diagrams and/or flowchart
diagrams, and combinations of blocks in the block diagrams and/or
flowchart diagrams, can be implemented by special purpose
hardware-based systems that perform the specified functions or
acts, or combinations of special purpose hardware and program
code.
[0059] Instances in this specification where one element is
"coupled" to another element can include direct and indirect
coupling. Direct coupling can be defined as one element coupled to
and in some contact with another element. Indirect coupling can be
defined as coupling between two elements not in direct contact with
each other, but having one or more additional elements between the
coupled elements. Further, as used herein, securing one element to
another element can include direct securing and indirect securing.
Additionally, as used herein, "adjacent" does not necessarily
denote contact. For example, one element can be adjacent another
element without being in contact with that element.
[0060] As used herein, the phrase "at least one of", when used with
a list of items, means different combinations of one or more of the
listed items may be used and only one of the items in the list may
be needed. The item may be a particular object, thing, or category.
In other words, "at least one of" means any combination of items or
number of items may be used from the list, but not all of the items
in the list may be required. For example, "at least one of item A,
item B, and item C" may mean item A; item A and item B; item B;
item A, item B, and item C; or item B and item C. In some cases,
"at least one of item A, item B, and item C" may mean, for example,
without limitation, two of item A, one of item B, and ten of item
C; four of item B and seven of item C; or some other suitable
combination.
[0061] In the above description, certain terms may be used such as
"up," "down," "upper," "lower," "horizontal," "vertical," "left,"
"right," "over," "under" and the like. These terms are used, where
applicable, to provide some clarity of description when dealing
with relative relationships. But, these terms are not intended to
imply absolute relationships, positions, and/or orientations. For
example, with respect to an object, an "upper" surface can become a
"lower" surface simply by turning the object over. Nevertheless, it
is still the same object. Further, the terms "including,"
"comprising," "having," and variations thereof mean "including but
not limited to" unless expressly specified otherwise. An enumerated
listing of items does not imply that any or all of the items are
mutually exclusive and/or mutually inclusive, unless expressly
specified otherwise. The terms "a," "an," and "the" also refer to
"one or more" unless expressly specified otherwise. Further, the
term "plurality" can be defined as "at least two."
[0062] The subject matter of the present disclosure may be embodied
in other specific forms without departing from its spirit or
essential characteristics. The described embodiments are to be
considered in all respects only as illustrative and not
restrictive. The scope of the invention is, therefore, indicated by
the appended claims rather than by the foregoing description. All
changes which come within the meaning and range of equivalency of
the claims are to be embraced within their scope.
* * * * *