TECHNICAL FIELD
[0001] The present subject matter relates, in general, to an exhaust gas recirculation
(EGR) system for a diesel engine and, particularly but not exclusively, to an exhaust gas
recirculation (EGR) system for diesel engines used in stationary applications.
BACKGROUND
[0002] An internal combustion diesel engine, also known as a compression-ignition
engine, uses the heat of compression of air for ignition of diesel fuel. Typically, the fuel is
injected into a combustion chamber where it gets ignited due to the heat of compression, and
subsequently undergoes combustion. Generally, diesel engines are used in mobile
applications, such as heavy load transport, due to their longevity and lower operating costs.
Modern diesel engines, hereinafter referred to as engines, are quiet and generally require
much less maintenance than other engines. However, diesel engines emit exhaust gases which
typically include harmful gases, especially mono-nitrogen oxides comprising nitric
oxide (NO) and nitrogen dioxide (NO2), commonly known as NOX emissions.
[0003] Worldwide, stringent emission legislations have been imposed on exhaust
gases emitted from diesel engines to reduce the content of harmful gases, such as NOX, in the
emissions. One of the popular techniques used for reducing NOX formation in the combustion
chamber, and thereby reducing NOX in the emissions, of the diesel engine is Exhaust gas
recirculation (EGR). In EGR, a part of the exhaust gas from the diesel engine after the
combustion of fuel is re-circulated into the diesel engine through an EGR valve coupled to an
exhaust manifold and an intake manifold of the diesel engine. However, since EGR can result
in reduced combustion temperature, change in air-fuel ratio, and loss of engine power, it has
to be controlled based on engine running conditions. Typically, the exhaust gas recirculation
into the diesel engine is controlled by an electronic controller, also known as Electronic
Control Unit (ECU), through the EGR valve based on the engine running conditions, such as
engine speed and accelerator position.
SUMMARY
[0004] This summary is provided to introduce concepts related to regulating exhaust
gas recirculation in diesel engine for stationary application. This summary is not intended to
identify essential features of the claimed subject matter nor is it intended for use in
determining or limiting the scope of the claimed subject matter.
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[0005] In accordance with an embodiment of the present subject matter methods and
systems for controlling exhaust gas recirculation in diesel engine for stationary application,
are described. The method includes obtaining operating loads of the diesel engine and a
temperature of one of exhaust gas and boost gas from the diesel engine. The temperature of
one of exhaust gas and boost gas, and the operating loads are analysed to determine whether
the temperature of one of exhaust gas and boost gas have reached predetermined threshold
values. Based on the analysis, an exhaust gas recirculation valve is controlled for controlling
exhaust gas recirculation into the diesel engine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The detailed description is described with reference to the accompanying
figures. In the figures, the left-most digit(s) of a reference number identifies the figure in
which the reference number first appears. The same numbers are used throughout the figures
to reference like features and components. Some embodiments of the method(s) in
accordance with the present subject matter are described, by way of example only, and with
reference to the accompanying figures, in which:
[0007] Fig. 1a schematically illustrates an exhaust gas recirculation system (EGR)
system in a diesel engine for stationary application, in accordance with an embodiment of the
present subject matter.
[0008] Fig. 1b schematically illustrates an exhaust gas recirculation system (EGR)
system in a naturally aspirated diesel engine for stationary application, in accordance with an
embodiment of the present subject matter.
[0009] Fig. 1c schematically illustrates an EGR system implemented in a
turbocharged diesel engine for stationary application, in accordance with one embodiment of
the present subject matter.
[0010] Fig. 1d illustrates an EGR system implemented in a turbocharged intercooled
diesel engine for stationary application, in accordance with one embodiment of the present
subject matter.
[0011] Fig. 1e illustrates an EGR system implemented in the turbocharged diesel
engine for stationary application, in accordance with another embodiment of the present
subject matter.
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[0012] Fig. 1f illustrates an EGR system implemented in the turbocharged intercooled
(TCI) diesel engine for stationary application, in accordance with another embodiment of the
present subject matter.
[0013] Fig. 2a illustrates a method of controlling EGR in diesel engines for stationary
application using temperature as one input, in accordance with the embodiments of the
present subject matter.
[0014] Fig. 2b illustrates correlation between the exhaust temperature and engine in
accordance with the embodiments of the present subject matter.
[0015] It should be appreciated by those skilled in the art that any block diagrams
herein represent conceptual views of exhaust gas recirculation system embodying the
principles of the present subject matter.
DETAILED DESCRIPTION
[0016] The present subject matter relates to a method for exhaust gas recirculation
(EGR) in a diesel engine for stationary applications and exhaust gas recirculation (EGR)
system thereof. The method and the EGR system of the present subject matter facilitates in
substantial reduction of NOX emissions from the diesel engine in stationary applications. The
Exhaust Gas Recirculation (EGR) is conventionally adopted to reduce -nitrogen oxides
(NOX) emissions. The EGR involves re-circulating a controllable proportion of the diesel
engine's exhaust back into the intake air.
[0017] Typically, when combustion temperatures exceed 2500 degree F, atmospheric
nitrogen begins to react with oxygen during combustion. This results in NOX, which plays a
major role in urban air pollution. Generally, to reduce the formation of NOX, the combustion
temperature is kept below the NOX formation threshold. The control of combustion
temperature may be achieved by re-circulating a small amount of exhaust gas through an
EGR valve. The EGR valve controls a passageway between the intake and exhaust manifolds.
When the EGR valve opens, differential pressure between intake and exhaust manifolds
allows exhaust gas flow through the EGR valve, into intake manifold. Further, exhaust gas
from the EGR valve, referred to as EGR gas, displaces a small part of incoming air and has a
quenching effect on combustion temperatures, which keeps NOX produced within acceptable
limit. As an added benefit, the EGR gas also reduces the engines octane requirement, which
in turn decreases the danger of detonation. The deliberate reduction of the oxygen available
5
in the cylinder during combustion, based on utilization of the EGR gas has a substantial effect
on the emission and performance of diesel engine.
[0018] In diesel engines for mobile application, for example, diesel engines of cars,
trucks, etc., an electronic control unit (ECU) is employed for control of EGR valve.
Typically, the ECU obtains engine running condition inputs, for example, engine speed and,
accelerator position for control of EGR valve to control the amount of exhaust gas being recirculated.
Further, in diesel engines with common rail systems, ECU inputs may also include
rate of air mass flow and rate of NOX generation. Based on such inputs, the ECU determines
unique and distinct operating condition of the diesel engine, and issues commands to the
EGR valve for controlling the flow of exhaust gas to the intake manifold. However, when
diesel engines are used as stationary engines, for example, as a diesel generator, the throttle
position is kept in fixed position to achieve constant engine speed. Further, the conventional
input parameters, such as engine load, used in automobile applications are unavailable due to
the distinct working conditions in stationary application, and may result in complicated,
ineffective and costly EGR systems for stationary applications.
[0019] The present subject matter discloses a method for controlling the EGR in the
diesel engine of stationary applications. In one implementation, the stationary application can
be a diesel generator set. In an implementation the diesel engine can be a naturally aspirated
engine, a turbocharged (TC) engine or a turbocharged and intercooled (TCI) engine. In one
embodiment of the present subject matter, an exhaust gas temperature is obtained and
provided as an input to the ECU. In another embodiment of the present subject matter, a
boost gas temperature is obtained and provided as an input to the ECU.
[0020] Since the diesel engine in the stationary applications operates at a single
speed, the temperature measurement is carried out at the single operating speed under
different operating load conditions. Further, the exhaust gas temperature in the diesel engine
changes with a change in operating load and therefore enables control of the EGR valve by
the ECU. In one implementation, the ECU activates the EGR valve when the exhaust gas
temperature is below a predefined exhaust gas temperature and allows EGR flow into the
diesel engine. The ECU does not allow the EGR flow into the diesel engine when the exhaust
gas temperature is at the predefined exhaust gas temperature corresponding to higher loads.
Thus, by controlling the EGR flow at higher loads, a cooling system heat rejection capacity in
the diesel engine can be maintained. As would be understood, heat rejection is the removal
of excess heat from the cooling system by a radiator. In addition to the temperature
6
measurement, frequency of an AC alternator coupled to the diesel engine is also measured
and provided to the ECU as an additional parameter. This additional parameter is used as a
safety measure in situations, for example, when the temperature measurement may be faulty.
[0021] As would be evident from above, the ECU controlled EGR maintains fuel
efficiency at higher loads by avoiding higher heat rejection capacity of the cooling system.
Further, the EGR control based on exhaust gas temperature is simple, easy to manufacture
and cost effective. These and other advantages of the present subject matter would be
described in greater detail in conjunction with the following figures.
[0022] While aspects of systems and method described for the EGR can be
implemented in any number of different diesel engines for stationary application, the
embodiments are described in the context of the following exemplary system(s). It should be
noted that the description merely illustrates the principles of the present subject matter. It will
thus be appreciated that those skilled in the art will be able to devise various arrangements
that, although not explicitly described herein, embody the principles of the present subject
matter and are included within its spirit and scope. Furthermore, all examples recited herein
are principally intended expressly to be only for pedagogical purposes to aid the reader in
understanding the principles of the invention and the concepts contributed by the inventor(s)
to furthering the art, and are to be construed as being without limitation to such specifically
recited examples and conditions. Moreover, all statements herein reciting principles, aspects,
and embodiments of the invention, as well as specific examples thereof, are intended to
encompass equivalents thereof.
[0023] The manner in which the system and the method for exhaust gas recirculation
(EGR) in diesel engines for stationary applications shall be implemented has been explained
in details with respect to the Fig. 1a-1f and Fig. 2a-2b. It will also be appreciated by those
skilled in the art that the words during and when as used herein are not exact terms that mean
an action takes place instantly upon an initiating action but that there may be some small but
reasonable delay, such as a propagation delay, between the initial action and the reaction that
is initiated by the initial action. Additionally, the word “connected” and “coupled” is used
throughout for clarity in the description and can include either a direct connection or an
indirect connection.
[0024] Fig. 1a schematically illustrates an EGR control system 100 implemented for
a diesel engine 102 used in stationary applications, in accordance with the present subject
7
matter. The diesel engine 102 is coupled to an AC alternator 104 through a shaft. As a result
of the coupling, the AC alternator 104 is rotated by the diesel engine 102, and generates
electrical power. The diesel engine 102 can be selected from one of a naturally aspirated, a
turbocharged, and a turbocharged and intercooled aspirations/versions. An EGR valve 106
allows recirculation of exhaust gas into the diesel engine 102. Examples of the EGR valve
106 include vacuum operated valve, solenoid operated valve, and so on. Also, the EGR valve
106 can be operated as NORMALLY OPEN (NO) or NORMALLY CLOSED (NC) based on
functional requirements. In one implementation, the EGR valve 106 can be coupled with an
intake pipe and an exhaust pipe. In another implementation, the EGR valve 106 can be
mounted on one of an intake manifold and an exhaust manifold. The amount of exhaust gas
entering an intake manifold through the EGR valve 106 is controlled by an ECU 108.
[0025] The ECU 108 controls opening and closing of the EGR valve 106 by obtaining
input parameters indicative of temperature of one of the exhaust gas and the boost gas and
operating load of the diesel engine 102. In one embodiment, the temperature of the exhaust
gas is obtained by measuring a temperature of the exhaust gas by a temperature sensor at an
exhaust manifold. In another embodiment, the temperature of the boost gas is obtained by
measuring a temperature of the boost gas by the temperature sensor at a compressor outlet of
turbocharger coupled to the exhaust manifold. In one implementation, the temperature sensor
can be a J-type thermocouple. Further, to provide a safety measure, AC frequency of the AC
alternator 104 can be provided as an additional input to the ECU 108. The control of the EGR
valve 106 is further based on analysis of the input parameters by the ECU 108. In one
implementation, the ECU 108 is preloaded with a representative data which represents a
correlation between temperature of exhaust gas and operating load of diesel engine 102. The
representative data also indicates a pre-determined threshold value of the temperature of
exhaust gas and a maximum load value of operating load. The ECU 108 analyzes the input
parameters by comparing the input parameters with the representative data. Based on the
analysis, the ECU 108 closes the EGR valve 106 when the temperature of the exhaust gas
reaches the pre-determined threshold value and the operating load conditions are nearing the
maximum load value. The controlling of the EGR valve 106 is further explained with
reference to Fig 2a and 2b.
[0026] Fig. 1b schematically illustrates an EGR control system 100 implemented for a
naturally aspirated diesel engine 110 in stationary application according to one embodiment
of the present subject matter. In an implementation, the stationary application can be a diesel
8
generator set. The naturally aspirated diesel engine 110 is coupled to the AC alternator 104
through a shaft 112. The naturally aspirated diesel engine 110 rotates the AC alternator 104
for generating electrical power. The naturally aspirated diesel engine 110 has an intake
manifold 114 for allowing fresh air into the naturally aspirated diesel engine 110 through an
intake pipe 115. The intake pipe 115 is coupled to an air filter which filters the fresh air prior
to flowing into the naturally aspirated diesel engine 110. The naturally aspirated diesel engine
110 has an exhaust manifold 116 for removing exhaust gas out of the naturally aspirated
diesel engine 110. The exhaust gas is re-circulated into the intake manifold 114 directly from
the exhaust manifold 116 through an exhaust pipe 118-1 & EGR valve 106. As would be
understood, the exhaust pipe 118-1 is coupled with the intake pipe 115 such that exhaust gas
mixes with the fresh air prior to flowing into the naturally aspirated diesel engine 110. The
EGR valve 106 is coupled with the exhaust pipe 118-1 for allowing the exhaust gas into the
intake manifold 114. The amount of exhaust gas entering the intake manifold 114 through the
EGR valve 106 coupling the exhaust pipe 118-1 is controlled by the ECU 108. According to
the embodiment, the ECU 108 controls the EGR valve 106 by obtaining temperature of
exhaust gas through a temperature sensor 120 mounted on the exhaust manifold 116.
[0027] Fig. 1c schematically illustrates EGR control system 100 implemented for a
turbocharged (TC) diesel engine 122 in stationary application, according to one embodiment
of the present subject matter. In the embodiment, the TC diesel engine 122 is coupled to the
AC alternator 104 through the shaft 112. The TC diesel engine 122 rotates the AC alternator
104 for generating electrical power. The intake manifold 114 allows intake air into the TC
diesel engine 122 and the exhaust manifold 116 removes the exhaust gas from the TC diesel
engine 122. A part of the exhaust gas from exhaust manifold 116 is fed into the intake
manifold 114 through the exhaust pipe 118-1 coupled to the EGR valve 106 controlled by the
ECU 108. As would be understood, the amount of exhaust gas fed into the intake manifold
114 depends on engine requirements. In one implementation, the EGR valve 106 can be
provided on the exhaust pipe 118-1. In another implementation, the EGR valve 106 can be
mounted on one of the intake manifold 114 and the exhaust manifold 116. Another part of the
exhaust gas from the exhaust manifold 116 drives a turbine (T) of a turbocharger that in turn
drives compressor (C) of turbocharger. After driving the turbine (T) of turbocharger, the
exhaust gas exits into atmosphere. For the ease of reference, the compressor (C) and the
turbine (T) of turbocharger are depicted in the figure as CT 124. Compressor (C) compresses
fresh air received from an air cleaner through the intake pipe 115 and feeds compressed air
9
into intake manifold 114 through a boost pipe 118-2 coupled to the intake pipe 115. As would
be understood, this compressed air is also termed as the boost gas. According to the
embodiment, the ECU 108 controls the EGR valve 106 by obtaining exhaust gas temperature
through the temperature sensor 120 mounted on the exhaust manifold 116.
[0028] Fig. 1d schematically illustrates EGR control system 100 implemented for a
TCI diesel engine 126 in stationary application, according to one embodiment of the present
subject matter. In the embodiment, the TCI diesel engine 126 is coupled to the AC alternator
104 through the shaft 112. The TCI diesel engine 126 rotates the AC alternator 104 for
generating electrical power. The intake manifold 114 allows intake air into the TCI diesel
engine 126 and the exhaust manifold 116 removes the exhaust gas from the TCI diesel engine
126. A part of exhaust gas from the exhaust manifold 116 is fed into the intake manifold 114
through the exhaust pipe 118-1 coupled to the EGR valve 106 which is controlled by ECU
108. As would be understood, the amount of exhaust gas fed into the intake manifold 114
depends on engine requirements. In one implementation, the EGR valve 106 can be provided
on the exhaust pipe 118-1. In another implementation, the EGR valve 106 can be provided on
one of the intake manifold 114 and the exhaust manifold 116. Another part of the exhaust gas
from exhaust manifold 116 drives the turbine (T) of turbocharger that in turn drives
compressor (C) of turbocharger. After driving the turbine (T) of the turbocharger, the exhaust
gas exits into atmosphere. For the ease of reference, the compressor (C) and the turbine (T) of
turbocharger are depicted in the figure as CT 124. Compressor (C) compresses fresh air
received from the air cleaner through the intake pipe 115 and feeds the compressed air to an
intercooler 128. The compressed air is then fed into the intake manifold 114 through the
boost pipe 118-2. As would be understood, this compressed air is also termed as the boost
gas. According to the embodiment, the ECU 108 controls the EGR valve 106 by obtaining
exhaust gas temperature through the temperature sensor 120 mounted on the exhaust
manifold 116.
[0029] Fig. 1e schematically illustrates EGR control system 100 implemented for the
TC diesel engine 122 in stationary application, according to another embodiment of the
present subject matter. In the embodiment, the TC diesel engine 122 is coupled to the AC
alternator 104 through the shaft 112. The TC diesel engine 122 rotates the AC alternator 104
for generating electrical power. The intake manifold 114 allows fresh air into the TC diesel
engine 122 and the exhaust manifold 116 removes the exhaust gas from the TC diesel engine
122. A part of the exhaust gas from the exhaust manifold 116 is fed into the intake manifold
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114 through the exhaust pipe 118-1 coupled to the EGR valve 106 which is controlled by
ECU 108. As would be understood, the amount of exhaust gas fed into the intake manifold
114 depends on engine requirements. In one implementation, the EGR valve 106 can be
provided on the exhaust pipe 118-1. In another implementation, the EGR valve 106 can be
provided on one of the intake manifold 114 and the exhaust manifold 116Another part of the
exhaust gas from exhaust manifold 116 drives the turbine (T) of turbocharger that in turn
drives the compressor (C) of turbocharger 124. After driving the turbine (T) of turbocharger,
exhaust gas exits into the atmosphere. For the ease of reference, the compressor (C) and the
turbine (T) of turbocharger are depicted in the figure as CT 124. Compressor (C) compresses
fresh air received from the air cleaner through the intake pipe 115 and feeds compressed air
to intake manifold 114 through the boost pipe 118-2. As would be understood, this
compressed air is also termed as the boost gas. According to the embodiment, the ECU 108
controls the EGR valve 106 by obtaining boost gas temperature through the temperature
sensor 120 mounted on the boost pipe 118-2.
[0030] Fig. 1f schematically illustrates EGR control system 100 implemented for the
TCI diesel engine 126 in stationary application, according to one embodiment of the present
subject matter. In the embodiment, the TCI diesel engine 126 is coupled to the AC alternator
104 through the shaft 112. The TCI diesel engine 126 rotates the AC alternator 104 for
generating electrical power. The intake manifold 114 allows air into the TCI diesel engine
126 and the exhaust manifold 116 removes the exhaust gas from the TCI diesel engine 126. A
part of the exhaust gas from the exhaust manifold 116 is fed into the intake manifold 114
through the exhaust pipe 118-1 coupled to the EGR valve 106 which is controlled by ECU
108. As would be understood, the amount of exhaust gas fed into the intake manifold 114
depends on engine requirements. In one implementation, the EGR valve 106 can be provided
on the exhaust pipe 118-1. In another implementation, the EGR valve 106 can be provided on
one of the intake manifold 114 and the exhaust manifold 116. Another part of the exhaust gas
from exhaust manifold 116 drives the turbine (T) of turbocharger that in turn drives
compressor (C) of turbocharger. After driving the turbine (T) of turbocharger, exhaust gas
exits into the atmosphere. For the ease of reference, the compressor (C) and the turbine (T) of
turbocharger are depicted in the figure as CT 124. Compressor (C) compresses fresh air
received from the air cleaner through the intake pipe 115 and feeds the compressed air to the
intercooler 128. The compressed air is then fed into the intake manifold 114 through the
boost pipe 118-2. As would be understood, this compressed air is also termed as the boost
11
gas. According to the embodiment, the ECU 108 controls the EGR valve 106 by obtaining
boost gas temperature through the temperature sensor 120 mounted on the boost pipe 118-2..
[0031] Fig. 2 illustrates a method 200 of controlling EGR in diesel engines for
stationary application using temperature as one input, in accordance with the embodiments of
the present subject matter. The order in which the method 200 is described is not intended to
be construed as a limitation, and any number of the described method blocks can be
combined in any order to implement the method 200, or alternative method. Additionally,
individual blocks may be deleted from the method 200 without departing from the spirit and
scope of the subject matter described herein. In an example, the method 200 may be
implemented in an EGR control system, such as an EGR control system 100.
[0032] As discussed previously, the temperature of the exhaust gas and the boost gas
increases as the operating load increases and vice-versa. The opening and closing of the EGR
valve 106 is controlled according to the operating load conditions and in turn the temperature
conditions. Accordingly, a threshold temperature is predetermined for opening the EGR valve
106 below certain operating load conditions and stored in ECU 108.
[0033] To determine the setting temperature, the diesel engine 102 is tested on an
engine dynamometer. As would be understood by those skilled in the art, the ECU 108
receives only the temperature as the input when the diesel engine 102 is tested with the
engine dynamometer. The load on the diesel engine is divided into five categories for
example 100%, 75%, 50%, 25% and 10% with 100% load being indicative of a threshold
load value, and the temperature is measured at each of the loads. Based on the engine
requirement the threshold value is decided and the EGR valve 106 is closed when the load
value has reached the threshold load value. A representative data including a correlation
between the measured temperatures and operating loads is determined and loaded in the ECU
108. The threshold temperature is determined based on the correlation, for example, as a
temperature sensed between threshold load value say 100% load and second load value say
75% load. After the threshold temperature is determined, the diesel engine 102 is coupled
with the AC alternator 104 for generating electrical power commercially. In one
implementation, the ECU 108 is designed with “OR Function Gate” logic such that EGR
valve 106 can be controlled based on availability of either one of the temperature input and
AC frequency input or both the inputs. It would be understood the ECU 108 can be designed
based on logic most suitable for providing temperature inputs.
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[0034] Referring to method 200, at block 202 temperature of one of exhaust gas and
boost gas from the diesel engine and operating loads of the diesel engine 102 when coupled
with the AC alternator 104 are provided to the ECU 108. In one embodiment, the exhaust gas
temperature is obtained by the temperature sensor 120 mounted on the exhaust manifold 116
and provided to the ECU 108. In another embodiment, the boost gas temperature is obtained
by the temperature sensor 120 mounted on the discharge of compressor (C) of the
turbocharger, depicted in Fig 1c-1f as CT 124, and provided to the ECU 108. Also, the AC
frequency of the AC alternator 104 may be provided to the ECU 108 to determine the
operating load conditions of the diesel engine 102.
[0035] At block 204, the temperature of one of exhaust gas and boost gas, and the
operating loads are analyzed by the ECU 108 for determining if at least one of the
temperature of one of exhaust gas and boost gas and the operating loads reaches
predetermined threshold values.
[0036] At block 206, the EGR valve 106 is controlled by the ECU 108 to enable
effective EGR based on the analysis. Based on the analysis, the ECU 108 closes EGR valve
106 when the temperature of one of exhaust gas and boost gas and the operating loads
reaches the threshold values. In one implementation, the EGR valve 106 is closed when the
temperature of the exhaust gas reaches the pre-determined threshold temperature. In one
implementation, the EGR valve 106 is closed when the temperature of the boost gas reaches
the pre-determined threshold temperature. In another implementation, the EGR valve 106 is
closed when the operating loads are nearing the threshold load value. Further, based on the
analysis, the ECU 108 opens the EGR valve 106 when the temperature of the exhaust gas is
less than the pre-determined threshold temperature and the operating load conditions are less
than the threshold load value. Further, the ECU 108 compares the temperature of one of
exhaust gas and boost gas and the operating loads with the predetermined representative data.
In one implementation, the ECU 108 may close the EGR valve 106 when the temperature of
one of exhaust gas and boost gas does not reach the pre-determined threshold temperature but
the operating load conditions are nearing the threshold load value. Thus, a fail-safe
mechanism for closing the EGR valve 106 is created to control the EGR in case the
temperature sensor 120 malfunctions. Thus, the closing of EGR valve 106 at higher operating
loads improves fuel efficiency and smoke.
[0037] Fig 2b illustrates correlation between the exhaust temperature and engine load
based on the above method in one implementation. Curve 208 depicts increase in exhaust
13
temperature when operating loads of engine increase when EGR technique is employed.
Further, the exhaust temperatures are reduced when the EGR valve 106 is closed at threshold
load value. This provides benefit in terms of Brake Specific Fuel Consumption (BSFC) and
smoke that get reduced when the EGR valve 106 is closed. Column 210 provides the status of
the EGR valve 106 and columns 212, 214, and 216 provides sample values of smoke, BFSC
and exhaust temperature observed when the diesel engine 102 speed is say 1500 rpm and
operating load is say 100%,. As can be interpreted from the sample values, the value of
smoke is reduced by 84.5%, the value of BFSC is reduced by 1.5%, and the exhaust
temperature is reduced by 6.5% when the EGR valve 106 is closed. It should be appreciated
that the benefit of reduced BFSC and smoke are dependent on the amount of EGR introduced
into the diesel engine.
[0038] Although embodiments for the EGR control system have been described in the
language specific to structural features, it is to be understood that the invention is not
necessarily limited to the specific features described. Rather, the specific features are
disclosed and explained in the context of a few embodiments of the EGR control system.
[0039] The EGR control system of the present subject matter is not restricted to the
embodiments that are mentioned above in the description. Although the subject matter has
been described with reference to the specific embodiments, this description is not meant to be
construed in limiting sense. Various modifications of the disclosed embodiments, as well as
alternate embodiments of the subject matter, will become apparent to person skilled in the art
upon reference to the description of the subject matter. It is therefore contemplated that such
modifications can be made without departing from the spirit or the scope of the present
subject matter as defined.
14
I/We claim:
1. A method for controlling exhaust gas recirculation in a diesel engine (102, 110, 122,
126) for stationary application, the method comprising:
obtaining temperature of one of exhaust gas and boost gas by a temperature
sensor (120) mounted on at least one of an exhaust manifold (116) and a boost pipe
(118-2), wherein the exhaust manifold (116) is coupled with the diesel engine (102,
110, 122, 126);
obtaining operating load of the diesel engine (102, 110, 122, 126),
analyzing the obtained temperature of one of exhaust gas and boost gas and
the operating load by the ECU (108); and
controlling an exhaust gas recirculation (EGR) valve (106) coupled with an
exhaust pipe (118-1) of the diesel engine (102, 110, 122, 126) by the ECU (108)
based on the analysis when at least one of the temperature of one of exhaust gas and
boost gas and operating load reach predetermined threshold values.
2. The method as claimed in claim 1, further comprising:
comparing the temperature of one of exhaust gas and boost gas and the
operating load with a predetermined representative data, wherein the predetermined
representative data indicates correlation between the temperature of exhaust gas and
the operating load of the diesel engine (102, 110, 122, 126).
3. The method as claimed in claim 1, wherein the controlling exhaust gas recirculation
by the ECU (108) further comprises:
closing the EGR valve (106) when the temperature of one of exhaust gas and
boost gas reaches a threshold temperature.
4. The method as claimed in claim 1, wherein the controlling exhaust gas recirculation
by the ECU (108) further comprises:
closing the EGR valve (106) coupled when the operating load of the diesel
engine (102, 110, 122, 126) reaches a threshold load value.
5. A system for exhaust gas recirculation in a diesel engine (102, 110, 122, 126) coupled
to an AC alternator 104 for stationary applications, wherein the diesel engine (102, 110, 122,
126) rotates the AC alternator 104 for generating electrical power, the system comprising:
15
an intake manifold (114) connected to the diesel engine (102, 110, 122, 126);
an exhaust manifold (116) connected to the diesel engine (102, 110, 122, 126);
a temperature sensor (120) mounted on one of the exhaust manifold (116) and
a boost pipe (118-2) for providing a temperature of one of exhaust gas and boost gas;
and
an electronic control unit (ECU) (108) coupled to the temperature sensor (120)
for controlling an exhaust gas recirculation (EGR) valve (106) based on the data
received from the temperature sensor (120), wherein the EGR valve is coupled with
an intake manifold (114) and the exhaust manifold (116).
6. The system as claimed in claim 5, wherein the ECU (108) closes the EGR valve (106)
when the temperature of one of exhaust gas and boost gas reaches a threshold temperature.
7. The system as claimed in claim 5, wherein the ECU (108) further receives a
frequency signal from AC alternator 104 for providing a frequency data indicative of
operating load of the diesel engine (102, 110, 122, 126).
8. The system as claimed in claim 7, wherein the ECU (108) closes the EGR valve (106)
when the operating load of the diesel engine (102, 110, 122, 126) has reached a threshold
load value.
9. The system as claimed in claim 5, wherein the diesel engine (102, 110, 122, 126) is
one of a naturally aspirated diesel engine, a turbocharged diesel engine, and a turbocharged
intercooled diesel engine.
10. The system as claimed in claim 5, wherein the EGR valve (106) is provided on one of
the intake manifold 114, the exhaust manifold 116, and the exhaust pipe 118-1 .