TECHNICAL FIELD
[0001] The present disclosure relates to, generally, to an internal combustion engines
and, more specifically, to a method and a system for increasing catalyst operating
temperature during hot engine and catalyst operating conditions for a Bi-fuel vehicle
operating in gas mode to control/reduce methane (CH4) emissions.
BACKGROUND
[0002] Background description includes information that may be useful in
understanding the present invention. It is not an admission that any of the information
provided herein is prior art or relevant to the presently claimed invention, or that any
publication specifically or implicitly referenced is prior art.
[0003] Pollutants produced by exhaust from internal combustion engines are of major
concern. These pollutants include hydrocarbon, carbon monoxide (CO), nitrogen oxide
(NOx), methane (CH4), and particulate emissions. The type and amount of emissions
depend, among other things, on the type of engine, fuel system, and other operating
conditions. For example, diesel engines produce relatively low amounts of CO but
produce significant amounts of particulate matter in the form of soot, that is comprised of
carbon, ash, that is comprised of inorganics, and polynuclear aromatic hydrocarbons
(PAHs), that are condensed about the carbon nuclei of the soot. NOx emissions are also a
significant problem for diesel engines.
[0004] NOx emissions arise from reactions occurring during the combustion process
which involve nitrogen present in the combustion air (atmospheric nitrogen) or, to a lesser
extent, bound in the fuel (fuel-bound nitrogen). NOx formation from atmospheric nitrogen
is the dependent on the temperature at which combustion occurs. In other words, the
greater the temperature in the combustion chamber, the greater the resultant NOx
emissions will be. Conversion of fuel-bound nitrogen to NOx depends on the amount and
reactivity of the nitrogen compounds in the fuel and on the amount of oxygen present.
[0005] The total hydrocarbon (THC) include the methane fraction as well as non-
methane hydrocarbon emissions. The methane is a strong greenhouse gas therefore there
are regulation to control the emission of methane gas upto a predefined limit. In the natural
gas operated vehicles, methane emission is distinguished as a separate emission from the
THC. Therefore, there is a requirement to control the emission of methane into the
environment. To convert methane into acceptable gas, expensive methane catalysts are
required.
[0006] Further, the existing catalytic converter can reduce the emission of methane
after achieving a particular temperature which is more than light off temperature of the
catalytic converter. Therefore, a method and a system is required which can raise the
temperature of catalytic converter to reduce methane emission with controlling NOx
emissions.
OBJECTS OF THE DISCLOSURE
[0001] Some of the objects of the present disclosure, which at least one
embodiment herein satisfy, are listed herein below.
[0002] The principal object of the present invention is to provide a method and a
system to reduce methane emissions from internal combustion engine by increasing
temperature of the catalytic converter.
[0003] Another object of the present invention is to provide rich and lean fuel ratio
in alternating combustion cylinders.
[0004] Another object of the present invention is to provide a method and a system
25 to reduce methane emissions in natural gas running vehicles where base air-fuel ratio
is 0.98 & 0.985.
[0005] These and other objects and advantages will become more apparent when
reference is made to the following description and accompanying drawings.
SUMMARY
[0007] This summary is provided to introduce concepts related to reduction of
5 methane emission from internal combustion engines. The concepts are further described
below in the detailed description. This summary is not intended to identify key features
or essential features of the claimed subject matter, nor is it intended to be used to limit the
scope of the claimed subject matter.
[0008] In an embodiment, a method for increasing temperature of catalytic converter
of an exhaust gas system to reduce methane emissions. The method comprising
determining temperature difference (Td) between target temperature (Tg) of the
catalytic converter and current temperature (Tcc) of the catalytic converter and based
on the temperature difference (Td), when there is requirement to raise the temperature
of the catalytic converter, selects a predetermined air-fuel ratio (λ) for each cylinder of
an internal combustion engine from the pre-stored list. In the air-fuel ratio (λ) in first
cylinder is rich and in second cylinder is lean according to firing order of the internal
combustion engine to increase operating temperature of the catalytic converter.
[0009] In an embodiment, the method includes selecting lean value of the air-fuel
ratio (λ) for the first cylinder and calculating rich value of the air-fuel ratio (λ) based
on the lean value so that total of the rich and the lean air-fuel ratio gives base air-fuel
ratio (λ).
[0010] In an aspect, the base air-fuel ratio (λ) is 0.98.
[0011] In an aspect, the method further comprise determining temperature of
coolant (Tc) and temperature of catalytic converter (Tcc) and ascertain whether the
25 temperature of coolant (Tc) is greater than predefined threshold temperature (Th1) and
the temperature of catalytic converter (Tcc) is greater than predefined threshold
temperature (Th2).
[0012] In an aspect, the internal combustion engine is in natural gas mode.
[0013] In an aspect, the method includes ascertaining whether catalyst health and
rear O2 voltage of the catalytic converter are above predefine threshold values.
[0014] In an aspect, the method includes controlling emission of NOx during the
5 lean air-fuel ratio by capturing the emission of NOx in reserve chamber (R1) and
recirculating the captured emission of NOx into the catalytic converter.
[0015] In another embodiment, an engine control unit (ECU) is coupled with an
internal combustion engine, air intake system, and exhaust gas system to increase
temperature of catalytic converter of the exhaust gas system to reduce methane
emissions. The ECU comprise an engine control module (ECM) to determine
temperature difference (Td) between target temperature (Tg) of the catalytic converter
and current temperature (Tcc) of the catalytic converter. Based on the temperature
difference (Td), when a temperature of the catalytic converter is to be raised, select a
predetermined air-fuel ratio (λ) from the pre-stored database for each cylinder of an
15 internal combustion engine (102), where the air-fuel ratio (λ) in first cylinder is rich
and in second cylinder is lean according to firing order of the internal combustion
engine to increase operating temperature of the catalytic converter.
[0016] In an aspect, the ECU selects lean value of the air-fuel ratio (λ) for the first
cylinder and calculating rich value of the air-fuel ratio (λ) based on the lean value so
20 that total of the rich and the lean air-fuel ratio gives base air-fuel ration (λ).
[0017] In an aspect, the ECU determines temperature of coolant (Tc) and
temperature of catalytic converter (Tcc) and ascertain whether the temperature of
coolant (Tc) is greater than predefined threshold temperature (Th1) and the temperature
of catalytic converter (Tcc) is greater than predefined threshold temperature (Th2).
25 [0018] In an aspect, the ECU control emission of NOx during the lean air-fuel ratio
by capturing the emission of NOx in reserve chamber (R1) and recirculating the
captured emission of NOx into the catalytic converter.
5
[0019] Various objects, features, aspects, and advantages of the inventive subject
matter will become more apparent from the following detailed description of preferred
embodiments, along with the accompanying drawing figures in which like numerals
represent like components.
5 BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The illustrated embodiments of the subject matter will be best understood by
reference to the drawings, wherein like parts are designated by like numerals throughout.
The following description is intended only by way of example, and simply illustrates
certain selected embodiments of devices, systems, and processes that are consistent with
10 the subject matter as claimed herein, wherein:
[0021] FIG. 1 illustrates an exemplary block diagram of a system having engine
control unit to control internal combustion engine, in accordance with an embodiment
of the present disclosure;
[0022] FIG. 2 illustrate an exemplary method implementing a system, to reduce
15 methane emissions, in accordance with an embodiment of the present disclosure; and
[0023] FIG. 3 illustrate controlling NOx emissions while lean fueling the internal
combustion engine, in accordance with an embodiment of the present disclosure.
[0024] The figures depict embodiments of the present subject matter for the
purposes of illustration only. A person skilled in the art will easily recognize from the
20 following description that alternative embodiments of the structures and methods
illustrated herein may be employed without departing from the principles of the
disclosure described herein.
DETAILED DESCRIPTION
[0025] The detailed description of various exemplary embodiments of the
25 disclosure is described herein with reference to the accompanying drawings. It should
be noted that the embodiments are described herein in such details as to clearly
6
communicate the disclosure. However, the amount of details provided herein is not
intended to limit the anticipated variations of embodiments; on the contrary, the
intention is to cover all modifications, equivalents, and alternatives falling within the
scope of the present disclosure as defined by the appended claims.
5 [0026] It is also to be understood that various arrangements may be devised that,
although not explicitly described or shown herein, embody the principles of the present
disclosure. Moreover, all statements herein reciting principles, aspects, and
embodiments of the present disclosure, as well as specific examples, are intended to
encompass equivalents thereof.
10 [0027] The terminology used herein is for the purpose of describing particular
embodiments only and is not intended to be limiting of example embodiments. As used
herein, the singular forms “a",” “an” and “the” are intended to include the plural forms
as well, unless the context clearly indicates otherwise. It will be further understood that
the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein,
15 specify the presence of stated features, integers, steps, operations, elements and/or
components, but do not preclude the presence or addition of one or more other features,
integers, steps, operations, elements, components and/or groups thereof.
[0028] It should also be noted that in some alternative implementations, the
functions/acts noted may occur out of the order noted in the figures. For example, two
20 figures shown in succession may, in fact, be executed concurrently or may sometimes
be executed in the reverse order, depending upon the functionality/acts involved.
[0029] In addition, the descriptions of "first", "second", “third”, and the like in the
present invention are used for the purpose of description only, and are not to be
construed as indicating or implying their relative importance or implicitly indicating
25 the number of technical features indicated. Thus, features defining "first" and "second"
may include at least one of the features, either explicitly or implicitly.
[0030] Unless otherwise defined, all terms (including technical and scientific terms)
7
used herein have the same meaning as commonly understood by one of ordinary skill
in the art to which example embodiments belong. It will be further understood that
terms, e.g., those defined in commonly used dictionaries, should be interpreted as
having a meaning that is consistent with their meaning in the context of the relevant art
5 and will not be interpreted in an idealized or overly formal sense unless expressly so
defined herein.
[0031] FIG. 1 illustrates an example block diagram of a system to reduce methane
emissions in accordance with an embodiment of the present disclosure. The system
includes an engine control unit 100, an internal combustion engine 102, air intake
10 system 101 and exhaust system 103. In an example, the internal combustion engine 104
is a gasoline engine that can run on combined natural gas (CNG) also. The internal
combustion engine 102 may have odd number of cylinders or may have even number
of cylinders. The internal combustion engine 102 receives fresh air from the air intake
system 101. In the natural gas running mode, the internal combustion engine receives
15 air-fuel mixture from the air intake system 101. The exhaust gas system 103 includes
an exhaust pipe having a catalytic converter to convert emission into acceptable form.
Further, the exhaust gas system may include an Exhaust Gas Recirculation (EGR)
system 102 in conjunction with an internal combustion engine to re-circulate the
emissions for further treatment.
20 [0032] In the ECU 100 an engine control module (ECM) 104 and a data base 105 is
provided. The ECM 104 controls functions and working of the internal combustion
engine 102 based on the inputs received and controls the exhaust gas system 103 to
control the emissions. The data base 105 stores all pre-stored information required for
processing of the system and working of the internal combustion engine 102 according
25 on the present invention along with other features. The ECM 104 is communicatively
coupled to the internal combustion engine 102, the air intake system 101, and the
exhaust gas system. The ECM 104 is communicatively coupled with a plurality of
sensors and a plurality of valves at various location in the internal combustion engine
8
102, at the air intake system 101, and at the exhaust gas system 103 to receive and send
input and instructions for operations.
[0033] FIG. 1 illustrates an example of the ECU 100 for controlling methane
emissions by supplying lean air fuel mixture to one of the cylinders of internal
5 combustion engine and controlling the exhaust flow entering the transfer tube system
to restrict NOx getting expelled out in the vehicle tail pipe without reprocessing in
accordance with an example of the present disclosure. The ECU 100 may be implemented
as a standalone device communicatively connected through a network to other devices
such as air intake system 101, internal combustion engine 102, exhaust gas system 103,
10 and the like.
[0034] The ECU 100 may include an interface(s), an engine control module (ECM)
104 and database 105. The interface(s) may provide a communication pathway for one
or more components of the ECU 100. The ECM 104 may be implemented as a
combination of hardware and programming (for example, programmable instructions)
15 to implement one or more functionalities of the ECM 104. In examples described
herein, such combinations of hardware and programming may be implemented in
several different ways. For example, the programming for the ECM 104 may be
processor executable instructions stored on a non-transitory machine-readable storage
medium and the hardware for the ECM 104 may include a processing resource (for
20 example, one or more processors), to execute such instructions. In the present
examples, the machine-readable storage medium may store instructions that, when
executed by the processing resource, implement the ECM 104. In such examples, the
ECU 100 may include the machine-readable storage medium storing the instructions
and the processing resource to execute the instructions, or the machine-readable storage
25 medium may be separate but accessible to the ECU 100 and the processing resource.
In other examples, the ECM 104 may be implemented by electronic circuitry.
[0035] The ECM 104 receives inputs related to coolant temperature ‘Tc’ and current
catalytic temperature ‘Tcc’. The ECM 104 compares the received coolant temperature
9
‘Tc’ with a predefined threshold value ‘Th1’ and compare the current catalytic
temperature ‘Tcc’ with a predefined threshold value ‘Th2’. When the coolant
temperature ‘Tc’ is above the predefined threshold value ‘Th1’ which is threshold
temperature, for example, 80 degrees and the current catalytic temperature ‘Tcc’ is
5 above the predefined threshold value ‘Th2’ which is temperature, for example, Lightoff
temperature of the catalytic converter, the ECM 104 determines temperature difference
‘Td’ between the current catalytic temperature ‘Tcc’ and the target temperature ‘Tg’.
The target temperature ‘Tg’ of the catalytic converter is the temperature where methane
(CH4) breaks into acceptable form, such as CO2. The database 105 includes the
10 predefined threshold values ‘Th1’, ‘Th2’ and target temperature ‘Tg’. Further, the
ECM 104 stores received and calculated information into the database 105 for further
processing.
[0036] Upon determining the temperature difference ‘Td’, the ECM 104 confirms
that there is no misfire in the internal combustion engine. The ECM 104 also checks
15 whether the internal combustion engine is not operating in very higher predetermined
load points where catalytic converter protection enrichment is required. The ECM 104
checks whether the internal combustion engine is not operating at very low
predetermined load points when exhaust flow is very low. The ECM 104 also check
whether the internal combustion engine is not in transient operation. Upon affirmative
20 confirmation from various checks, the ECM 104 determine catalyst health and rear O2
sensor voltage.
[0037] When the catalyst health and rear O2 sensor voltage is greater than the
predefined threshold value ‘Th3’, when temperature of the catalytic converter is to be
raised, the ECM 104 selects a predetermined air-fuel ratio (λ) from the database
25 corresponding to the temperature difference ‘Td’.
10
S.
No.
1
2
Temperature difference (Td in degrees)
0-50
0-50 [ IF NOX IS NOT PRODUCED @
STEADY OPERATING CONDITION ]
50-100[ 50 > 100/150/200/]
DYNAMIC Lean value
(in % of base lambda
value)
0.75% -> 1.5 % -> 0.75
%[ SYSTEM WILL
CONTINUE TO
OPERATE LEANER
TILL NOX IS NOT
PRODUCED , Ie NO
DIP IN SOX VOLTAGE
BEFORE AND START
OF SYSTEM LEANESS
BELOW PREDEFINED
VALUE
1.25% -> 2.5 % -> 1.25%
1.75% -> 3.5 -> 1.75%
[ SYSTEM WILL
CONTINUE TO
OPERATE LEANER
TILL NOX IS NOT
PRODUCED , Ie NO
DIP IN SOX VOLTAGE
BEFORE AND START
OF SYSTEM LEANESS
BELOW PREDEFINED
VALUE
11
50-100[ 50 > 100/150/200/] [ IF NOX IS NOT
PRODUCED IN SL 3 @ STEADY
OPERATING CONDITION ]
2.25% -> 4.5 -> 2.25%
[0038] The ECM 104 selects the lean value from the pre-stored data to apply the
air-fuel ratio (λ) in the internal combustion engine. In the present internal combustion
engine base air fuel ratio (λ) is 0.98. The ECM 104 selects the air-fuel ratio (λ) for each
5 cylinder of the internal combustion engine, where the air-fuel ratio (λ) in first cylinder
is rich and in second cylinder is lean according to firing order of the internal
combustion engine. The present internal combustion engine 102 can have even number
of cylinders or can have odd number of cylinders. For both the odd and the even number
of cylinders of the internal combustion engine 102, the lean value is distributed with
10 respect to firing order of the internal combustion engine. Considering even number (4)
cylinders in the engine:
1s t cylinder C1
R1% Rich
2nd cylinder C2
L1% Lean
3rd cylinder C3
R2% Rich
4th cylinder C4
L2 % Lean
For example: If the predetermined lean value is 2% for a temperature difference of
50o, the cylinder 2 and 4 will have below mentioned air-fuel ratio
15 L1 and L2 is = 0.98 X.98 [ BASE ]
R1 and R2 is = 1.01 X0.98[ BASE]
In the above equations where base lambda is 0.98, the air fuel ratio is lean by 2% in the
cylinder 2 and 4; and the air-fuel ratio is rich by 2% in the cylinder 1 and 3.
[0039] The ECM 104 selects lean value of the air-fuel ratio (λ) for the first cylinder
20 C1 and calculates rich value of the air-fuel ratio (λ) based on the lean value for the
12
second cylinder C2 and the dip in the rear O2 voltage [if any] with respect to to
predefined threshold before after system leanness at steady state vehicle operation so
that total of the rich and the lean air-fuel ratio does not worse base emission.
[0040] Referring to fig. 3, upon executing the rich and lean air fuel ratio in alternate
5 firing cylinders in the internal combustion engine, the ECM 104 opens valves V1 and
V2 of the EGR system in the exhaust gas system 103. The valve V1 is located before
the catalytic converter ‘CC’ and the valve V2 is located after the catalytic converter.
During the execution, dynamic fuel leanness in alternate firing cylinders, there is high
chances of NOx emission generation as system is being shifted to leaner side with
10 respect to the base lambda 0.98. The ECM 104 operates valves V1 and V2 in a
predefined opening combination with respect to exhaust flow and engine operating
condition, and entrap the NOx produced in last lean event in a emission reserve
chamber ‘R1’ which is located between the valve V1 and the valve V2.
[0041] The NOx produced during lean operation from base lambda =0.98, is
15 captured and stored in the reserve R1 and later recirculated back into the catalytic
converter ‘CC’ using the Valve V1 as per the predefined selection to control the NOx.
[0042] Once the target temperature ‘Tg’ of the catalytic converter is achieved, the
ECM 104 disables injection of rich and lean air-fuel mixture in the cylinders of the
internal combustion engine.
20 [0043] An additional NOx Sensor is also incorporated before and after the catalytic,
which judges the NOx emission during the period Lean fueling.
[0044] With the integrated operation of Nox Sensor Lean burn operation in CNG
mode is achieved.
[0045] FIG. 2 illustrates an example method 300 for increasing temperature of
25 catalytic converter of an exhaust gas system (103) to reduce methane emissions in
accordance with an embodiment of the present disclosure. The order in which the
method 300 is described is not intended to be construed as a limitation, and any number
13
of the described method blocks may be combined in any order to implement the
methods, or an alternative method. Furthermore, method 300 may be implemented by
processing resource or ECU 100 through any suitable hardware, non-transitory
machine-readable instructions, or combination thereof.
5 [0046] At block 302, the method includes determining temperature of coolant (Tc)
and temperature of catalytic converter (Tcc).
[0047] At block 304, the method includes ascertaining whether the temperature of
coolant (Tc) is greater than predefined threshold temperature (Th1) and the temperature
of catalytic converter (Tcc) is greater than predefined threshold temperature (Th2).
10 When the temperature of coolant (Tc) is greater than predefined threshold temperature
(Th1) and the temperature of catalytic converter (Tcc) is greater than predefined
threshold temperature (Th2), the method proceeds to block 306. If any of the condition
is not satisfied, the method proceeds back to block 302.
[0048] At block 306, the method includes determining temperature difference (Td)
15 between target temperature (Tg) of the catalytic converter and current temperature
(Tcc) of the catalytic converter.
[0049] At block 308, the method includes ascertaining whether catalyst health and
rear O2 sensor voltage of the catalytic converter are above predefine threshold values.
After ascertainment, the method proceeds to block 310.
20 [0050] At block 312, the method includes selecting a predetermined/predefined airfuel
ratio (λ) for each cylinder of an internal combustion engine (102), where the airfuel
ratio (λ) in first cylinder is rich and in second cylinder is lean according to firing
order of the internal combustion engine (102) to increase operating temperature of the
catalytic converter based on the temperature difference (Td) and when there is
25 requirement to increase the temperature of the catalytic converter.
[0051] At block 312, the method includes controlling emission of NOx during the
lean air-fuel ratio by capturing the emission of NOx in reserve chamber (R1) and
14
recirculating the captured emission of NOx into the catalytic converter.
[0052] In an aspect, lean value of the air-fuel ratio (λ) for the first cylinder and
calculating rich value of the air-fuel ratio (λ) based on the lean value so that total of the
rich and the lean air-fuel ratio gives base air-fuel ration (λ).
5 [0053] In an aspect, the base air-fuel ratio (λ) is 0.98.
[0054] In an aspect, the internal combustion engine 102 is in natural gas mode.
[0055] The above description does not provide specific details of manufacture or
design of the various components. Those of skill in the art are familiar with such details,
and unless departures from those techniques are set out, techniques, known, related art
10 or later developed designs and materials should be employed. Those in the art are
capable of choosing suitable manufacturing and design details.
[0056] It should be understood, however, that all of these and similar terms are to
be associated with the appropriate physical quantities and are merely convenient labels
applied to these quantities. Unless specifically stated otherwise, as apparent from the
15 discussion herein, it is appreciated that throughout the description, discussions utilizing
terms such as “processing,” or “ascertaining,” or “receiving,” or “actuating,” or
“determining,” “defining,” or the like, refer to the action and processes of a computer
system, or similar electronic computing device, that manipulates and transforms data
represented as physical (electronic) quantities within the computer system's registers
20 and memories into other data similarly represented as physical quantities within the
computer system memories or registers or other such information storage, transmission
or display devices.
[0057] Further, the terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of the disclosure. It will
25 be appreciated that several of the above-disclosed and other features and functions, or
alternatives thereof, may be combined into other systems or applications. Various
presently unforeseen or unanticipated alternatives, modifications, variations, or
15
improvements therein may subsequently be made by those skilled in the art without
departing from the scope of the present disclosure as encompassed by the following
claims.
[0058] The claims, as originally presented and as they may be amended, encompass
5 variations, alternatives, modifications, improvements, equivalents, and substantial
equivalents of the embodiments and teachings disclosed herein, including those that
are presently unforeseen or unappreciated, and that, for example, may arise from
applicants/patentees and others.
[0059] Although examples for the present disclosure have been described in
10 language specific to structural features and/or methods, it should be understood that the
appended claims are not necessarily limited to the specific features or methods
described. Rather, the specific features and methods are disclosed and explained as
examples of the present disclosure.

We claim:
1. A method for increasing catalyst operating temperature, the method comprising:
determining (306) temperature difference (Td) between target temperature
(Tg) of the catalytic converter and current temperature (Tcc) of the catalytic
5 converter; and
based on the temperature difference (Td), selecting (310) a predefined airfuel
ratio (λ) for each cylinder of an internal combustion engine (102), where the
air-fuel ratio (λ) in first cylinder is rich and in second cylinder is lean according
to firing order of the internal combustion engine (102) to increase operating
temperature of the catalytic converter.
2. The method as claimed in claim 1, wherein the selecting (310) lean value of the
air-fuel ratio (λ) for the first cylinder and calculating rich value of the air-fuel ratio (λ)
based on the lean value so that total of the rich and the lean air-fuel ratio gives base air-
fuel ration (λ).
3. The method as claimed in claim 2, wherein the base air-fuel ratio (λ) is 0.98.
4. The method as claimed in claim 1, wherein the method further comprises:
determining (302) temperature of coolant (Tc) and temperature of catalytic
converter (Tcc); and
ascertaining (304) whether the temperature of coolant (Tc) is greater than
predefined threshold temperature (Th1) and the temperature of catalytic
converter (Tcc) is greater than predefined threshold temperature (Th2); and
upon ascertainment selecting (312) the predetermined air-fuel ratio (λ).
5. The method as claimed in claim 1, wherein the internal combustion engine (102)
is in natural gas mode.
6. The method as claimed in claim 1, wherein the method further comprises:
ascertaining (308) whether catalyst health and rear O2 sensor voltage of the
catalytic converter are above predefine threshold values.
7. The method as claimed in claim 1, wherein the method further comprises:
controlling (314) emission of NOx during the lean air-fuel ratio by
capturing the emission of NOx in reserve chamber (R1) and recirculating the
captured emission of NOx into the catalytic converter.
8. An engine control unit (ECU) (100) coupled with an internal combustion engine
(102), air intake system (101) and exhaust gas system (103) to increase temperature of
catalytic converter of the exhaust gas system (103) to reduce methane, the ECU (100)
comprising:
an engine control module (ECM) (104) to:
determine temperature difference (Td) between target temperature
(Tg) of the catalytic converter and current temperature (Tcc) of the catalytic
converter;
based on the temperature difference (Td), when a temperature of the
catalytic converter is to be raised, select a predetermined air-fuel ratio (λ)
from the pre-stored database (105) for each cylinder of an internal
combustion engine (102), where the air-fuel ratio (λ) in first cylinder is rich
20 and in second cylinder is lean according to firing order of the internal
combustion engine (102) to increase operating temperature of the catalytic
converter.
9. The ECU (100) as claimed in claim 8, wherein the ECM (104) selects lean value
of the air-fuel ratio (λ) for the first cylinder and calculating rich value of the air-fuel
ratio (λ) based on the lean value so that total of the rich and the lean air-fuel ratio gives
base air-fuel ration (λ).
10. The ECU (100) as claimed in claim 8, wherein the base air-fuel ratio (λ) is 0.98.
11. The ECU (100) as claimed in claim 8, wherein the ECM (104) is to:
determine temperature of coolant (Tc) and temperature of catalytic
converter (Tcc); and
ascertain (304) whether the temperature of coolant (Tc) is greater than
predefined threshold temperature (Th1) and the temperature of catalytic
converter (Tcc) is greater than predefined threshold temperature (Th2); and
upon ascertainment select the predetermined air-fuel ratio (λ).
12. The ECU (100) as claimed in claim 8, wherein the internal combustion engine
(102) is in natural gas mode.
13. The ECU (100) as claimed in claim 8, wherein the ECM (104) is to:
control emission of NOx during the lean air-fuel ratio by capturing the
emission of NOx, using an additional Nox sensor (), in reserve chamber (R1) and
recirculating the captured emission of NOx into the catalytic converter.