An Overview of CI Engine Emission Control Notes | EduRev

: An Overview of CI Engine Emission Control Notes | EduRev

 Page 1


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture26/26_1.htm[6/15/2012 3:06:10 PM]
 Module 6:Emission Control for CI Engines
 Lecture 26:An Overview of CI Engine Emission Control
The Lecture Contains:
EMISSION CONTROL IN CI ENGINES
AN OVERVIEW OF CONTROL OF CI ENGINE EMISSIONS
Page 2


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture26/26_1.htm[6/15/2012 3:06:10 PM]
 Module 6:Emission Control for CI Engines
 Lecture 26:An Overview of CI Engine Emission Control
The Lecture Contains:
EMISSION CONTROL IN CI ENGINES
AN OVERVIEW OF CONTROL OF CI ENGINE EMISSIONS
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture26/26_2.htm[6/15/2012 3:06:10 PM]
 Module 6:Emission Control for CI Engines
 Lecture 26:An Overview of CI Engine Emission Control
 
AN OVERVIEW OF CONTROL OF CI ENGINE EMISSIONS
For emission control in the CI engines, usually called as the diesel engines the following are important;
CI engines emits pollutants in solid (soot), liquid (poly aromatic hydrocarbons, fuel and oil
components, sulphur acids) as well as those in gaseous (CO, HC, NO
x
) state.
Emissions of nitrogen oxides and particulate matter from diesel engines are of main concern.
Emission regulations do have limits for CO and HC as well from the CI engines, but
 concentration of their emissions is rather small and these have been relatively easy to control
through improved engine and fuel system design.
NO
x
 - PM  trade off (discussed in Module 2) governs selection and optimization of many engine
design variables e.g, injection timing, injection pressure, boost pressure  etc as change in some
engine variables may although causes reduction in NO
x
 but increases PM and vice versa.
Engine design changes to reduce NO
x
 emissions many a times result also in higher brake
specific fuel consumption (BSFC). This is important as the emissions of the greenhouse gas,
CO
2
 are also to be reduced.
The development efforts like for the SI engines have been focused on reduction of engine-out
emissions and treatment of the exhaust gases. Improvements in fuel quality also have been made to
meet the needs of advanced emission control technology.
In CI engines, mixture formation and combustion is heterogeneous and complex in nature. It is
governed by;      
 
 
 
 
 
 
 
 
 
 
 
 
Page 3


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture26/26_1.htm[6/15/2012 3:06:10 PM]
 Module 6:Emission Control for CI Engines
 Lecture 26:An Overview of CI Engine Emission Control
The Lecture Contains:
EMISSION CONTROL IN CI ENGINES
AN OVERVIEW OF CONTROL OF CI ENGINE EMISSIONS
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture26/26_2.htm[6/15/2012 3:06:10 PM]
 Module 6:Emission Control for CI Engines
 Lecture 26:An Overview of CI Engine Emission Control
 
AN OVERVIEW OF CONTROL OF CI ENGINE EMISSIONS
For emission control in the CI engines, usually called as the diesel engines the following are important;
CI engines emits pollutants in solid (soot), liquid (poly aromatic hydrocarbons, fuel and oil
components, sulphur acids) as well as those in gaseous (CO, HC, NO
x
) state.
Emissions of nitrogen oxides and particulate matter from diesel engines are of main concern.
Emission regulations do have limits for CO and HC as well from the CI engines, but
 concentration of their emissions is rather small and these have been relatively easy to control
through improved engine and fuel system design.
NO
x
 - PM  trade off (discussed in Module 2) governs selection and optimization of many engine
design variables e.g, injection timing, injection pressure, boost pressure  etc as change in some
engine variables may although causes reduction in NO
x
 but increases PM and vice versa.
Engine design changes to reduce NO
x
 emissions many a times result also in higher brake
specific fuel consumption (BSFC). This is important as the emissions of the greenhouse gas,
CO
2
 are also to be reduced.
The development efforts like for the SI engines have been focused on reduction of engine-out
emissions and treatment of the exhaust gases. Improvements in fuel quality also have been made to
meet the needs of advanced emission control technology.
In CI engines, mixture formation and combustion is heterogeneous and complex in nature. It is
governed by;      
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture26/26_3.htm[6/15/2012 3:06:10 PM]
 Module 6:Emission Control for CI Engines
 Lecture 26:An Overview of CI Engine Emission Control
 
contd...
Mixture formation which depends on interactions between the injection spray, air motion and
combustion chamber geometry.
Air motion – swirl, squish etc,
Injection spray formation -precise control of fuel injection process is necessary for formation of
the desired spray and fuel atomization.
Combustion chamber type- Indirect Injection or Direct Injection. The indirect injection engines are
being phased out of production due to their poor fuel efficiency.
Intake boost pressure
     Turbocharging especially with variable boost pressure coupled with EGR results in substantial
reductions in both the NO
x
 and PM. 
   Exhaust aftertreatment such as diesel particulate filter (DPF), diesel oxidation catalysts (DOC),
selective catalytic reduction (SCR) of NO
x
 etc., are already in use. 
      An overview of various technologies and direction of research and development which have been
pursued to control NO
x
 and PM emissions from the CI engines are presented in Figs. 6.1 and 6.2
respectively.
 
 
 
 
 
 
 
 
 
 
 
 
 
Page 4


Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture26/26_1.htm[6/15/2012 3:06:10 PM]
 Module 6:Emission Control for CI Engines
 Lecture 26:An Overview of CI Engine Emission Control
The Lecture Contains:
EMISSION CONTROL IN CI ENGINES
AN OVERVIEW OF CONTROL OF CI ENGINE EMISSIONS
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture26/26_2.htm[6/15/2012 3:06:10 PM]
 Module 6:Emission Control for CI Engines
 Lecture 26:An Overview of CI Engine Emission Control
 
AN OVERVIEW OF CONTROL OF CI ENGINE EMISSIONS
For emission control in the CI engines, usually called as the diesel engines the following are important;
CI engines emits pollutants in solid (soot), liquid (poly aromatic hydrocarbons, fuel and oil
components, sulphur acids) as well as those in gaseous (CO, HC, NO
x
) state.
Emissions of nitrogen oxides and particulate matter from diesel engines are of main concern.
Emission regulations do have limits for CO and HC as well from the CI engines, but
 concentration of their emissions is rather small and these have been relatively easy to control
through improved engine and fuel system design.
NO
x
 - PM  trade off (discussed in Module 2) governs selection and optimization of many engine
design variables e.g, injection timing, injection pressure, boost pressure  etc as change in some
engine variables may although causes reduction in NO
x
 but increases PM and vice versa.
Engine design changes to reduce NO
x
 emissions many a times result also in higher brake
specific fuel consumption (BSFC). This is important as the emissions of the greenhouse gas,
CO
2
 are also to be reduced.
The development efforts like for the SI engines have been focused on reduction of engine-out
emissions and treatment of the exhaust gases. Improvements in fuel quality also have been made to
meet the needs of advanced emission control technology.
In CI engines, mixture formation and combustion is heterogeneous and complex in nature. It is
governed by;      
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture26/26_3.htm[6/15/2012 3:06:10 PM]
 Module 6:Emission Control for CI Engines
 Lecture 26:An Overview of CI Engine Emission Control
 
contd...
Mixture formation which depends on interactions between the injection spray, air motion and
combustion chamber geometry.
Air motion – swirl, squish etc,
Injection spray formation -precise control of fuel injection process is necessary for formation of
the desired spray and fuel atomization.
Combustion chamber type- Indirect Injection or Direct Injection. The indirect injection engines are
being phased out of production due to their poor fuel efficiency.
Intake boost pressure
     Turbocharging especially with variable boost pressure coupled with EGR results in substantial
reductions in both the NO
x
 and PM. 
   Exhaust aftertreatment such as diesel particulate filter (DPF), diesel oxidation catalysts (DOC),
selective catalytic reduction (SCR) of NO
x
 etc., are already in use. 
      An overview of various technologies and direction of research and development which have been
pursued to control NO
x
 and PM emissions from the CI engines are presented in Figs. 6.1 and 6.2
respectively.
 
 
 
 
 
 
 
 
 
 
 
 
 
Objectives_template
file:///C|/...%20and%20Settings/iitkrana1/My%20Documents/Google%20Talk%20Received%20Files/engine_combustion/lecture26/26_4.htm[6/15/2012 3:06:10 PM]
 Module 6:Emission Control for CI Engines
 Lecture 26:An Overview of CI Engine Emission Control
 
contd....
Figure 6.1
An overview of NO
x
 reduction
techniques in CI engines
The technologies used for control of PM emissions are presented on Fig. 6.2.  
Figure 6.2
An overview of PM reduction
techniques in CI engines
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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