Enission unit 2

INTERNAL COMBUSTION ENGINES
INTERNAL COMBUSTION ENGINES (ELECTIVE) (ME667)
(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
(ELECTIVE) (ME667) SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
Jagadeesha T, Assistant Professor, Department of Mechanical Engineering, Adichunchanagiri Institute of Technology, Chikmagalur
EMISSION REGULATION AND CONTROL SYSTEMS
There has been a great concern, in recent years, that the
There has been a great concern, in recent years, that the I C Engines are
I C Engines are
I C Engines are
I C Engines are responsible
responsible
responsible
responsible
for too much atmospheric pollution, which is
for too much atmospheric pollution, which is detrimental to human health &
detrimental to human health &
detrimental to human health &
detrimental to human health & environment.
environment.
environment.
environment.
Thus concerted efforts are being made t
Thus concerted efforts are being made to reduce the responsible pollutants emitted
o reduce the responsible pollutants emitted
from the exhaust syst
from the exhaust system without sacrificing power &
em without sacrificing power &
em without sacrificing power &
em without sacrificing power & fuel consumption.
fuel consumption.
fuel consumption.
fuel consumption.
Air pollution can be defined as an addition to our atmosphere of any material which will
have a deleterious effect on life upon our planet. B
have a deleterious effect on life upon our planet. Besides
esides
esides
esides IC
IC
IC
IC engines other sources
engines other sources
such as electric power stations, industrial and domestic fuel consumers also add
pollution.
pollution.
pollution.
pollution.
MECHANISM OF POLLUTANTS
MECHANISM OF POLLUTANTS FORMATION
FORMATION
FORMATION
FORMATION (VTU
(VTU
(VTU
(VTU JAN 2007)
JAN 2007)
JAN 2007)
JAN 2007)
(MAIN
(MAIN
(MAIN
(MAIN POLLUTANTS
POLLUTANTS
POLLUTANTS
POLLUTANTS EMITTED BY
EMITTED BY
EMITTED BY
EMITTED BY PETROL ENGINE
PETROL ENGINE
PETROL ENGINE
PETROL ENGINE (VTU
(VTU
(VTU
(VTU FEB 2006
FEB 2006
FEB 2006
FEB 2006))
))
))
))
Pollutants are produced
Pollutants are produced by the incomplete burning of the air
by the incomplete burning of the air
by the incomplete burning of the air
by the incomplete burning of the air-
-
-
-fuel mixture in the
fuel mixture in the
fuel mixture in the
fuel mixture in the
combustion chamber. The major pollutants emitted from the exhaust due to incomplete
combustion are:
combustion are:
combustion are:
combustion are:
Carbon monoxide (CO)
Hydrocarbons (HC)
Hydrocarbons (HC)
Hydrocarbons (HC)
Hydrocarbons (HC)
Oxides of nitrogen (NO).
Other products produced are acetyl
Other products produced are acetylene, aldehydes etc. If,
ene, aldehydes etc. If,
ene, aldehydes etc. If,
ene, aldehydes etc. If, however, combustion
however, combustion
however, combustion
however, combustion is
is
is
is
complete
complete
complete
complete-
-
-
- -
-
-
- the only products being expelled from the exhaust would be water vapour
the only products being expelled from the exhaust would be water vapour
which is harmless, and carbon dioxide, which is an inert gas and, as such it is not
directly harmful to humans.
CARBON MONOX
CARBON MONOX
CARBON MONOX
CARBON MONOXIDE (CO)
IDE (CO)
IDE (CO)
IDE (CO) :
:
:
:
It is a colour
It is a colour
It is a colour
It is a colour less gas of about the same density as air.
less gas of about the same density as air.
less gas of about the same density as air.
less gas of about the same density as air. It is a poisonous gas which,
It is a poisonous gas which,
when inhaled, replaces the oxygen in the blood stream so that the body’s metabolism
can not function correctly.
can not function correctly. Small amounts of CO concentrations, when brea
Small amounts of CO concentrations, when brea
Small amounts of CO concentrations, when brea
Small amounts of CO concentrations, when breathed in, slow
thed in, slow
thed in, slow
thed in, slow
down physical and mental activity and produces headaches, while large concentration
will kill.
will kill.
will kill.
will kill.

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
Mechanism of formation of CO
CO is intermediate product of combustion remains in exhaust if the oxidation of CO to
C0
C0
C0
C02
2
2
2 is not complete. Theoretical
is not complete. Theoretical
is not complete. Theoretical
is not complete. Theoretically , it can be said that petrol engine exhaust is free of
ly , it can be said that petrol engine exhaust is free of
CO if the air fuel ratio is 15. However, some CO is always present in the exhaust even
at lean mixture and can be as high as 1%.
at lean mixture and can be as high as 1%. CO is generally formed when the mixture is
CO is generally formed when the mixture is
rich in fuel. The amount
rich in fuel. The amount of CO formed increases the mixture becomes more and more
of CO formed increases the mixture becomes more and more
rich in fuel. A small amount of CO will come out of the exha
rich in fuel. A small amount of CO will come out of the exhaust
ust
ust
ust even when the mixture
even when the mixture
is slightly lean in fuel. This is due to the fact that equilibrium is not
is slightly lean in fuel. This is due to the fact that equilibrium is not est
est
est
established
ablished
ablished
ablished when the
when the
when the
when the
products pass to
products pass to
products pass to
products pass to the exhaust. At the high temperature developed during th
the exhaust. At the high temperature developed during th
the exhaust. At the high temperature developed during th
the exhaust. At the high temperature developed during the combustion
e combustion
e combustion
e combustion,
,
,
,
the products formed are unstable, and the following reactions take place before the
equilibrium i
equilibrium i
equilibrium i
equilibrium is established.
s established.
s established.
s established.
2H
2H
2H
2H2
2
2
2O
O
O
O+ O
+ O
+ O
+ O2
2
2
2 →
→
→
→ 2(1
2(1
2(1
2(1-
-
-
-y) H
y) H
y) H
y) H2
2
2
20 + 2yH
0 + 2yH
0 + 2yH
0 + 2yH2
2
2
2 + yO
+ yO
+ yO
+ yO2
2
2
2
where,
where,
where,
where, y is the fraction
y is the fraction
y is the fraction
y is the fraction of H
of H
of H
of H2
2
2
20
0
0
0 dissociated.
dissociated.
dissociated.
dissociated.
C+0
C+0
C+0
C+02
2
2
2 →
→
→
→ C0
C0
C0
C02
2
2
2 →
→
→
→ + (
+ (
+ (
+ (1
1
1
1-
-
-
-x)CO
x)CO
x)CO
x)CO2
2
2
2 +x CO +
+x CO +
+x CO +
+x CO + x/2 O
x/2 O
x/2 O
x/2 O2
2
2
2
As the products cool down to exhaust temperature, major part of CO reacts with oxygen
form CO
form CO
form CO
form CO2
2
2
2 However, a relatively small amount of CO will remain in exhaust, its
However, a relatively small amount of CO will remain in exhaust, its
concentration creasing with
concentration creasing with rich mixtures.
rich mixtures.
rich mixtures.
rich mixtures.
2. HYDROCARBONS (HC):
The unburnt hydrocarbons emission is the direct result of incomplete combustion. The
emission amount of hydrocarbon is closely related to design variables and combustion
chamber design and operating variables such as A
chamber design and operating variables such as A:F ratio, speed, load and mode of
:F ratio, speed, load and mode of
operation
operation
operation
operation as idling, running or accelerating.
as idling, running or accelerating.
as idling, running or accelerating.
as idling, running or accelerating. Surface to volume ratio and wall quenching
Surface to volume ratio and wall quenching
greatly affects in formation of HC.
greatly affects in formation of HC. Hydrocarbons, derived from unburnt fuel emitted, b
Hydrocarbons, derived from unburnt fuel emitted, b
Hydrocarbons, derived from unburnt fuel emitted, b
Hydrocarbons, derived from unburnt fuel emitted, by
y
y
y
exhausts, engine crankcase fumes
exhausts, engine crankcase fumes and vapour
and vapour
and vapour
and vapour escaping from the
escaping from the
escaping from the
escaping from the carburetor
carburetor
carburetor
carburetor are also
are also
are also
are also
harmful to health.
harmful to health.
harmful to health.
harmful to health.
Mechanism of formation of HC
Due to existence of local very rich mixture pockets at much lower temperatures than
combustion chambers, unburnt hydrocarbons may appear in the exhaust.The
hydrocarbons
hydrocarbons
hydrocarbons
hydrocarbons also appear due to flame quenching near the metallic walls.
also appear due to flame quenching near the metallic walls.

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
A significant portion of this unburnt hydrocarbon may burn during expansion and
exha
exha
exha
exhaust
ust
ust
ust strokes if the oxygen concentration and exhaust temperature is suitable for
strokes if the oxygen concentration and exhaust temperature is suitable for
complete oxidati
complete oxidati
complete oxidati
complete oxidation
on
on
on Otherwise a l
Otherwise a l
Otherwise a l
Otherwise a large amount of hydrocarbon will go out with the
arge amount of hydrocarbon will go out with the
exhaust gases.
exhaust gases.
exhaust gases.
exhaust gases.
3. OXIDES OF NITROGEN (NO):
Oxides of N
Oxides of N
Oxides of N
Oxides of N2
2
2
2 generally occur mainly in the form of NO and N0
generally occur mainly in the form of NO and N0
2
2
2 .
.
.
. These are generally
These are generally
These are generally
These are generally
formed at high temperature. Hence high temperature and availability of 0
2
2
2 are
are
are
are the main
the main
the main
the main
reason for the formation of N0 and NO
reason for the formation of N0 and NO2
2
2
2 .Many other oxides like N
.Many other oxides like N
.Many other oxides like N
.Many other oxides like N2
2
2
2O
O
O
O4,
4,
4,
4, N
N
N
N2
2
2
2O
O
O
O,
,
,
, N
N
N
N2
2
2
2O
O
O
O3
3
3
3 ,N
,N
,N
,N2
2
2
2O
O
O
O5
5
5
5
are also formed in low concentration but they decompose spontaneously at ambient
conditions of NO
conditions of NO
conditions of NO
conditions of NO2
2
2
2. The maximum NO
. The maximum NO
. The maximum NO
. The maximum NOx
x
x
x levels are observed with A:F ratios of about
levels are observed with A:F ratios of about
levels are observed with A:F ratios of about
levels are observed with A:F ratios of about 10%
10%
10%
10%
above stoichiometric.
above stoichiometric. Oxides of nitrogen and other obnoxious substances are produced
Oxides of nitrogen and other obnoxious substances are produced
in very small
in very small
in very small
in very small quantities
quantities
quantities
quantities and, in certain environments, can cause pollution
and, in certain environments, can cause pollution
and, in certain environments, can cause pollution
and, in certain environments, can cause pollution,
,
,
, while
while
while
while
prolonged exposure is dang
prolonged exposure is danger
er
er
erous to health.
ous to health.
ous to health.
ous to health.
Mechanism of formation of nitric oxide (
Mechanism of formation of nitric oxide (NO)
NO)
NO)
NO)
At high combustion temperatures, the following chemical reactions take place behi
At high combustion temperatures, the following chemical reactions take place behind
nd
nd
nd
the flame:
the flame:
the flame:
the flame:
N
N
N
N2
2
2
2+ O
+ O
+ O
+ O2
2
2
2 →
→
→
→ 2NO
2NO
2NO
2NO
N
N
N
N2
2
2
2+
+
+
+ 2H
2H
2H
2H2
2
2
2 O
O
O
O →
→
→
→ 2NO
2NO
2NO
2NO+2H
+2H
+2H
+2H2
2
2
2
Chemical equilibrium calculations show that a significant amount of NO will be formed
the end of combustion. The
the end of combustion. The majority of NO formed will however
majority of NO formed will however
majority of NO formed will however
majority of NO formed will however decompose at the low
decompose at the low
temperature
temperature
temperature
temperature of exhaust. But due to very low reaction rate at the exhaust temperature a
of exhaust. But due to very low reaction rate at the exhaust temperature a
part of NO form
part of NO form
part of NO form
part of NO formed
ed
ed
ed remains in exhaust. It is far in excess of the equilibrium composition
remains in exhaust. It is far in excess of the equilibrium composition
at that temperature as
at that temperature as t formation of NO freezes at low exhaust temperatures.
t formation of NO freezes at low exhaust temperatures.
t formation of NO freezes at low exhaust temperatures.
t formation of NO freezes at low exhaust temperatures. The NO
The NO
The NO
The NO
formation will be less in rich mixtures than in lean mixtures.
4.
4.
4.
4. SMOKE OR PARTICULATE
SMOKE OR PARTICULATE
Solid particles are usually formed by dehydrogenation, polymerisation and
agglome
agglome
agglome
agglomeration
ration
ration
ration.
.
.
. In the combustion
In the combustion
In the combustion
In the combustion process of different hydrocarbons, acetylene (C
process of different hydrocarbons, acetylene (C
process of different hydrocarbons, acetylene (C
process of different hydrocarbons, acetylene (C2
2
2
2H
H
H
H2
2
2
2)
)
)
) is
is
is
is
formed as intermediate product. These acetylene molecules after simultaneous

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
polymerisation
polymerisation
polymerisation
polymerisation dehydration
dehydration
dehydration
dehydration produce carbon particles, which are the main constituent of
produce carbon particles, which are the main constituent of
the particula
the particula
the particula
the particulate.
te.
te.
te.
5.
5.
5.
5. ALDEHYDES
ALDEHYDES
ALDEHYDES
ALDEHYDES:
:
:
: Due
Due
Due
Due to very slow chemical reaction during delay period in the diesel
to very slow chemical reaction during delay period in the diesel
engines, aldehydes are formed as intermediate products. In some parts of the spray the
aldehydes will be left
aldehydes will be left after the initial reactions. These aldehydes may be oxidised in the
after the initial reactions. These aldehydes may be oxidised in the
later part o
later part o
later part o
later part of the cycle, if the mixture temperature is high, and if there is sufficient oxygen.
f the cycle, if the mixture temperature is high, and if there is sufficient oxygen.
At heavy loads, due to lack of oxygen, an increase in aldehyde emission in the exhaust
is observed.
is observed.
is observed.
is observed.
Exhaust
Exhaust
Exhaust
Exhaust Pollutants Versus the A:F ratio:
Pollutants Versus the A:F ratio:
Figure shows ho
Figure shows ho
Figure shows ho
Figure shows how three main
w three main
w three main
w three main exhaust pollutant products (CO,HC and NO
exhaust pollutant products (CO,HC and NO
exhaust pollutant products (CO,HC and NO
exhaust pollutant products (CO,HC and NOX
X
X
X) vary from
) vary from
) vary from
) vary from
different air
different air
different air
different air-
-
-
-fuel ratio operating on either side of the stochiometric ratio for a very rich
fuel ratio operating on either side of the stochiometric ratio for a very rich
mixture (11:1) to very lean mixture (18:1).
The amount of CO produced in the exhaust
is about 8% for an 11: 1
is about 8% for an 11: 1 air
air
air
air-
-
-
-fuel, ratio, but
fuel, ratio, but
fuel, ratio, but
fuel, ratio, but
this percentage steadily decreases to zero
as the mixture is reduced to just beyond the
stoichiometric ratio (on the lean side).
HC produced in the exhaust gases amounts
to about 1100 parts per million (ppm) with a
rich 11: 1 air
rich 11: 1 air
rich 11: 1 air
rich 11: 1 air-
-
-
-fuel
fuel
fuel
fuel ratio and, as the mixture
ratio and, as the mixture
strength approaches the stoichiometric ratio, it progressively falls to around 500 ppm. A
further weakening of the mixture to 18: 1 air
further weakening of the mixture to 18: 1 air-
-
-
-fuel, ratio only reduces HC content to
fuel, ratio only reduces HC content to
approximately 350 ppm.
Oxides of nitrogen products for
Oxides of nitrogen products formed during combustion are very low at 100 ppm with a
med during combustion are very low at 100 ppm with a
rich air
rich air
rich air
rich air-
-
-
-fuel ratio of 11: 1. As the mixture strength approaches the stoichiornetric ratio it
fuel ratio of 11: 1. As the mixture strength approaches the stoichiornetric ratio it
rises fairly rapidly to 2000 ppm, and a further reduction of the mixture strength to 15: 1
peaks the oxides o
peaks the oxides o
peaks the oxides o
peaks the oxides of nitrogen to something like 2,300 ppm, weakening the mixture
f nitrogen to something like 2,300 ppm, weakening the mixture
beyond this point rapidly reduces it until, at an 18: 1 air
beyond this point rapidly reduces it until, at an 18: 1 air-
-
-
-fuel ratio, it is 1000 ppm.
fuel ratio, it is 1000 ppm.

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
SOURCES
SOURCES
SOURCES
SOURCES OF POLLUTANTS F
OF POLLUTANTS F
OF POLLUTANTS F
OF POLLUTANTS FROM
ROM
ROM
ROM SI
SI
SI
SI ENGINE
ENGINE
ENGINE
ENGINE ( VTU JULY
( VTU JULY
( VTU JULY
( VTU JULY 2007)
2007)
2007)
2007)
The following are the three main sources for
The following are the three main sources form which pollutants are emitted from the SI
m which pollutants are emitted from the SI
engine:
engine:
engine:
engine:
The crankcase
The crankcase
The crankcase
The crankcase. Where piston blow
. Where piston blow
. Where piston blow
. Where piston blow-
-
-
-by fumes and oil mist are vented to the
by fumes and oil mist are vented to the
atmosphere.
atmosphere.
atmosphere.
atmosphere.
The fuel system
The fuel system
The fuel system
The fuel system. Where evaporative emissions from the
. Where evaporative emissions from the
. Where evaporative emissions from the
. Where evaporative emissions from the carburetor
carburetor
carburetor
carburetor or petrol
or petrol
or petrol
or petrol
injection air intake and fuel tank are vente
injection air intake and fuel tank are vented to the atmosphere.
d to the atmosphere.
The exhaust system
The exhaust system
The exhaust system
The exhaust system. Where the products of incomplete combustion are expelled
. Where the products of incomplete combustion are expelled
from the tail pipe into the atmosphere.
Crankcase Emission
Crankcase Emission
Crankcase Emission
Crankcase Emission
The piston and its rings are designed to form a gas
The piston and its rings are designed to form a gas-
-
-
-tight seal between the sliding piston
tight seal between the sliding piston
and
and
and
and c
c
c
cylinder walls. However, in practice there will always be some compressed charge
ylinder walls. However, in practice there will always be some compressed charge
and burnt fumes
and burnt fumes
and burnt fumes
and burnt fumes escape during
escape during
escape during
escape during compression and
compression and
compression and
compression and power stroke to crankcase.
power stroke to crankcase.
power stroke to crankcase.
power stroke to crankcase. These
These
These
These
gases
gases
gases
gases are usually
are usually
are usually
are usually unburnt air
unburnt air
unburnt air
unburnt air-
-
-
-fuel mixture hydrocarbons, or burnt (or partially burnt)
fuel mixture hydrocarbons, or burnt (or partially burnt)
products o
products o
products o
products of combustion, C0
f combustion, C0
f combustion, C0
f combustion, C02
2
2
2,
,
,
, H
H
H
H2
2
2
2O
O
O
O (steam) or CO.
(steam) or CO.
(steam) or CO.
(steam) or CO. These products also contaminate the
These products also contaminate the
lubricating oils.
lubricating oils.
lubricating oils.
lubricating oils.

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
Evaporative Emission
Evaporative emissions account for 15 to 25% of total hydrocarbon emission from a
gasoline engine. The following are two main sources of eva
gasoline engine. The following are two main sources of evaporative emissions:
porative emissions:
porative emissions:
porative emissions:
The fuel tank
The fuel tank
The fuel tank
The fuel tank
The carburettor.
The carburettor.
The carburettor.
The carburettor.
(i)
(i)
(i)
(i) Fuel tank losses
Fuel tank losses
Fuel tank losses
Fuel tank losses. The main factors governing the tank emissions are fuel volatility
. The main factors governing the tank emissions are fuel volatility
and the ambient temperature but the tank design and location can also influence the
emissions as location affects the
emissions as location affects the temperature. Insulation of tank and vapour collection
temperature. Insulation of tank and vapour collection
systems have all been explored with a view to reduce the tank emission.
(ii)
(ii)
(ii)
(ii) Carburettor losses
Carburettor losses
Carburettor losses
Carburettor losses. Although most internally vented carburettors have
. Although most internally vented carburettors have
. Although most internally vented carburettors have
. Although most internally vented carburettors have an external
an external
an external
an external
vent which opens
vent which opens
vent which opens
vent which opens at idle throttle position
at idle throttle position
at idle throttle position
at idle throttle position, the existing pressure forces prevent outflow of
, the existing pressure forces prevent outflow of
vapours to the atmosphere. Internally vented carburettor may enrich the mixture which
in turn increases exhaust emission.
EXHAUST EMISSION
EXHAUST EMISSION
EXHAUST EMISSION
EXHAUST EMISSION
The different constituents which are exhausted from S.I. engine an
The different constituents which are exhausted from S.I. engine and different factors
d different factors
d different factors
d different factors
which will affect percentages of different constituents are discussed below:
Hydrocarbons (HC)
Hydrocarbons (HC)
Hydrocarbons (HC)
Hydrocarbons (HC)
The emission amount of HC (due to incomplete co
The emission amount of HC (due to incomplete combustion) is closely related to
mbustion) is closely related to
D
D
D
Design variables
esign variables
esign variables
esign variables, Operating variables and engine condition. T
, Operating variables and engine condition. T
, Operating variables and engine condition. T
, Operating variables and engine condition. The Surface to volume
he Surface to volume

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
ratio greatly
ratio greatly
ratio greatly
ratio greatly affects
affects
affects
affects the HC emission. Higher the S/V
the HC emission. Higher the S/V
the HC emission. Higher the S/V
the HC emission. Higher the S/V ratio, higher the HC emission
ratio, higher the HC emission
irrespective of whether mixture is rich or lean. When the Mixture supplied is lean or rich,
the flame propagation becomes weak which causes in turn c
the flame propagation becomes weak which causes in turn causes incomplete
auses incomplete
auses incomplete
auses incomplete
combustion and results in HC emission.
Carbon Mono oxide (HC)
If the oxidation of CO to CO is not complete, CO remains in the exhaust. It can be said
theoretically that, the petrol engine exhaust can be made free from CO by operating it
theoretically that, the petrol engine exhaust can be made free from CO by operating it at
at
at
at
A/F ratio = 15. However, some CO is always present in the exhaust even at lean
mixture and can be as high as 1 per cent. CO emissions are lowest during acceleration
and at steady speeds. They are, however, high during idling and reach maximum during
de
de
de
deceleration.
celeration.
celeration.
celeration.
Oxides o
Oxides o
Oxides o
Oxides of nitrogen (NO)
f nitrogen (NO)
f nitrogen (NO)
f nitrogen (NO)
Oxides of nitrogen occur mainly in the form of NO and NO and are generally formed at
high temperature.
high temperature.
high temperature.
high temperature. • The maximum NO levels are observed with A/F ratios of about 10
• The maximum NO levels are observed with A/F ratios of about 10
percent above stoichiometric
percent above stoichiometric.
.
.
. It has also been obse
It has also been obse
It has also been obse
It has also been observed that NO increases with
rved that NO increases with
increasing manifold pressure, engine load and compression ratio. This characteristic is
different from HC and CO emission which is nearly independent of engine load except
for idling and deceleration.
Lead emission
Lead emission
Lead emission
Lead emission
Lead emissio
Lead emissio
Lead emissio
Lead emissions come only from S.I. engines. In the fuel, lead is present as
ns come only from S.I. engines. In the fuel, lead is present as
ns come only from S.I. engines. In the fuel, lead is present as
ns come only from S.I. engines. In the fuel, lead is present as antiknock
antiknock
antiknock
antiknock
agents in SI Engine.
agents in SI Engine. It may not be possible to eliminate lead completely from all petrols
It may not be possible to eliminate lead completely from all petrols
immediately because a large number of existing engines rely upon the lubrication
provided b
provided b
provided b
provided by a lead film to prevent rapid wear of exhaust valve seats.
y a lead film to prevent rapid wear of exhaust valve seats.

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
S
S
S
SI ENGINE EMISSION CONTROL
I ENGINE EMISSION CONTROL
I ENGINE EMISSION CONTROL
I ENGINE EMISSION CONTROL ( VTU JULY 2007)
( VTU JULY 2007)
( VTU JULY 2007)
( VTU JULY 2007)
The main methods, among various methods, for S.I. engine emission control are:
Modification in the engine design and operating parameters.
Treatment of exhaust products of combustion.
Modification of the fuels.
Modification in the Engine Design and Operating Parameters
Modification of
Modification of
Modification of
Modification of combustion chamber involves avo
combustion chamber involves avo
combustion chamber involves avo
combustion chamber involves avoiding flame quenching zones
iding flame quenching zones
where combustion might otherwise be incomplete a
where combustion might otherwise be incomplete and resulting in high HC
nd resulting in high HC
emission. This includes:
emission. This includes: Reduction of surface to volume (SAT) ratio,
Reduction of surface to volume (SAT) ratio,
Reduction of surface to volume (SAT) ratio,
Reduction of surface to volume (SAT) ratio, R
R
R
Reduced
educed
educed
educed
space around piston ring
Lower compression ratio: Lower compression ratio reduces the quenching effect
by reducing the quenching area, thus reducing HC.Lo
by reducing the quenching area, thus reducing HC.Lower compression ratio also
wer compression ratio also
reduces NO emissions due to lower maximum temperature.
reduces NO emissions due to lower maximum temperature. Lower compression,
Lower compression,
Lower compression,
Lower compression,
however, reduces thermal efficiency and increases fuel consumption.
The exhaust gas coming out of exhaust ma
The exhaust gas coming out of exhaust manifold is treated to reduce JIC and CO
nifold is treated to reduce JIC and CO
emissions. The devices used to accomplish
emissions. The devices used to accomplish are After burner , Exhaust manifold reactor
are After burner , Exhaust manifold reactor
and Catalytic converter.
After
After
After
After-
-
-
-burner
burner
burner
burner:
:
:
: is a burner where air is supplied
is a burner where air is supplied
to the exhaust gases and mixture is burnt with
the help o
the help o
the help o
the help of ignition system. The HC and CO
f ignition system. The HC and CO
which are formed in the engine combustion
because of inadequate 02 and inadequate
time to burn are further brunt by providing air in a separate box, known as after
time to burn are further brunt by providing air in a separate box, known as after-
-
-
-burner.
burner.
burner.
burner.
Exhaust manifold reactor
Exhaust manifold reactor is a further development
is a further development
is a further development
is a further development of after
of after
of after
of after-
-
-
-burner where the design is
burner where the design is
changed so as to minimize the heat loss and to provide sufficient time for mixing of
exhaust and secondary air.
exhaust and secondary air. 3. Catalytic converter:
3. Catalytic converter:
A catalytic converter
A catalytic converter is a device which is placed in the vehicle exhaust system to r
is a device which is placed in the vehicle exhaust system to r
is a device which is placed in the vehicle exhaust system to r
is a device which is placed in the vehicle exhaust system to reduce
educe
educe
educe
HC and CO by oxidizing catalyst and NO by reducing catalyst.

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
Modification of the fuels
The ability of a fuel to burn in mixtures leaner than stoichiometric ratio is a rough
indication of its potential emission reducing characteristics and reduced fu
indication of its potential emission reducing characteristics and reduced fuel
el
el
el
consumption.
consumption.
consumption.
consumption. If gasoline is changed to propane as engine fuel CO emission can
If gasoline is changed to propane as engine fuel CO emission can
substantially be reduced with reduced HC and NO and in changing from propane to
methane the CO as well HC emission touch zero level and only the NO remains as a
significant fa
significant fa
significant fa
significant factor.• From pollution point of vi
ctor.• From pollution point of vi
ctor.• From pollution point of vi
ctor.• From pollution point of view
ew
ew
ew both
both
both
both methane and steam reformed
methane and steam reformed
hexane
hexane
hexane
hexane are very
are very
are very
are very attract
attract
attract
attractive fuels but we are unable to use at present for want of
ive fuels but we are unable to use at present for want of
technological progress.
CONTROL OF OXIDES OF NITROGEN
CONTROL OF OXIDES OF NITROGEN ( VTU July
( VTU July
( VTU July
( VTU July 07
07
07
07/JAN 07/Aug05/July06
/JAN 07/Aug05/July06
/JAN 07/Aug05/July06
/JAN 07/Aug05/July06)
)
)
)
The concentration
The concentration
The concentration
The concentration of oxides of nitrogen in the exhaust is closely related to the peak
of oxides of nitrogen in the exhaust is closely related to the peak
cycle temperature. The following are the three methods (investigated so f
cycle temperature. The following are the three methods (investigated so far) for
ar) for
ar) for
ar) for
reducing peak cycle tem
reducing peak cycle temperature and thereby reducing NO emission.
perature and thereby reducing NO emission.
Exhaust gas recirculation (EGR)
Exhaust gas recirculation (EGR) ( VTU
( VTU
( VTU
( VTU Jan 2007)
Jan 2007)
Jan 2007)
Jan 2007)
Catalyst
Catalyst
Catalyst
Catalyst ( VTU Aug 2005/ July 2006)
( VTU Aug 2005/ July 2006)
( VTU Aug 2005/ July 2006)
( VTU Aug 2005/ July 2006)
Water injection.
Water injection.
Water injection.
Water injection.( VTU Aug 2005/ July 2006)
( VTU Aug 2005/ July 2006)
( VTU Aug 2005/ July 2006)
( VTU Aug 2005/ July 2006)
EXHAUST GAS RECIRCULATION ( E G R )
This method is commonly used to reduce NO
This method is commonly used to reduce NOx
x
x
x in petrol as well as diesel engines. In S.I
in petrol as well as diesel engines. In S.I
engines, about 10 percent recirculation r
engines, about 10 percent recirculation reduces NO
educes NO
educes NO
educes NOx
x
x
x emission by 50 percent.
emission by 50 percent.
emission by 50 percent.
emission by 50 percent. U
U
U
Unfortu
nfortu
nfortu
nfortu
nately, the consequently poorer combustion directly increases HC emission and calls
for mixture enrichment to restore combustion regularity which gives a further indirect in
crease of both HC and CO.
Figure sho
Figure sho
Figure sho
Figure shows
ws
ws
ws the arrangement of exhaust gas recirculation (EGR) system. A portion
the arrangement of exhaust gas recirculation (EGR) system. A portion
(about 10 to 15%) of the exhaust gases is re
(about 10 to 15%) of the exhaust gases is re-
-
-
-circulated to cylinder intake charge, an
circulated to cylinder intake charge, an
circulated to cylinder intake charge, an
circulated to cylinder intake charge, and
d
d
d
this reduces the quantity of O
this reduces the quantity of O2
2
2
2 availa
availa
availa
available for combustion. The exhaust
ble for combustion. The exhaust
ble for combustion. The exhaust
ble for combustion. The exhaust gas for
gas for
gas for
gas for
recirculation is take
recirculation is taken through an orifice and passed through control valve for regulation
n through an orifice and passed through control valve for regulation
of the quantity of recirculation.

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
T
T
T
The effect of A/F ratio of NO
he effect of A/F ratio of NO
he effect of A/F ratio of NO
he effect of A/F ratio of NOx
x
x
x emis
emis
emis
emission taking EGR
sion taking EGR
sion taking EGR
sion taking EGR
parameter is shown in figure. It may be observed
that, maximum emission of NO takes place during
lean mixture limits when gas recirculation is least
effective. Whereas, for emission of hydro carbon
(HC) and carbon monoxide (CO) lean mixture is
preferred, 15 percent recycling
re
re
re
reduces NO
duces NO
duces NO
duces NOx
x
x
x by 80 percent but in creases HC and CO by 50 to 80%. These are t
by 80 percent but in creases HC and CO by 50 to 80%. These are t
by 80 percent but in creases HC and CO by 50 to 80%. These are t
by 80 percent but in creases HC and CO by 50 to 80%. These are two
wo
wo
wo
conflicting requirements of this emission control system and this problem has been
solved by adopting package system which have both NO and HC/CO control devices.
Catalyst.
Catalyst.
Catalyst.
Catalyst. A few types of catalysts have been tested to reduce the emission of NO
A few types of catalysts have been tested to reduce the emission of NO
A few types of catalysts have been tested to reduce the emission of NO
A few types of catalysts have been tested to reduce the emission of NOx
x
x
x,
,
,
, a
a
a
a
cop
cop
cop
copper catalyst has been used in the presence of CO for this purpose. The research is
per catalyst has been used in the presence of CO for this purpose. The research is
going on to develop a good catalyst.
going on to develop a good catalyst. The research is on for newer good catalyst.
The research is on for newer good catalyst.
Water injection.
Water injection.
Water injection.
Water injection. It has been observed that the specific fuel consumption decreases a
It has been observed that the specific fuel consumption decreases a
few pe
few pe
few pe
few percent at medium water injection rate. Attempts have been made to use water as a
rcent at medium water injection rate. Attempts have been made to use water as a
device for controlling the N0
device for controlling the N0x
x
x
x .
.
.
.This method, because of its complexity, is rarely used.
This method, because of its complexity, is rarely used.

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
TOTAL EMISSION CONTROL PACKAGES ( VTU Feb 2006)
We know that any method which
We know that any method which is use
is use
is use
is used to decrease NO tries to increase HC and CO
d to decrease NO tries to increase HC and CO
and vice
and vice
and vice
and vice-
-
-
-versa. Thus it is of paramount importance to develop a method/system which
versa. Thus it is of paramount importance to develop a method/system which
should reduce emissions of NO HC, CO to a desired level simultaneously. After a long
and detailed experimental study of various
and detailed experimental study of various possible systems, the following two
possible systems, the following two
systems/packages have been developed to achieve the required results
1. Thermal reactor package
2. Catalytic converter package.
Using this approach, the following are the three basic methods of emission control:
Thermal
Thermal
Thermal
Thermal reactors, which rely on homogeneous oxidation to control CO and HC;
reactors, which rely on homogeneous oxidation to control CO and HC;
Oxidation catalyst for CO and HC;
Dual catalyst system (here a reduction catalyst for NO and an oxidation catalyst
for CO and HC are connected in series).
Thermal reactor package:
Thermal reactor package: ( VTU
( VTU
( VTU
( VTU July 2007)
July 2007)
July 2007)
July 2007)
A thermal reactor is a chamber which is designed to provide adequate residence time
for allowing appreciable oxidation of CO and HC to take place. For enhancing the
conversion of CO to CO
conversion of CO to CO2
2
2
2 the exhaust temperature is increased by retarding the s
the exhaust temperature is increased by retarding the s
the exhaust temperature is increased by retarding the s
the exhaust temperature is increased by retarding the spark.
park.
park.
park.
Actual thermal
Actual thermal
Actual thermal
Actual thermal
reactor (made of
reactor (made of
reactor (made of
reactor (made of
high nickel steel)
high nickel steel)
high nickel steel)
high nickel steel)
that is used on a
that is used on a
that is used on a
that is used on a car
car
car
car
consists of two
consists of two
consists of two
consists of two
enlarged exhaust
enlarged exhaust
enlarged exhaust
enlarged exhaust
manifolds which
manifolds which
manifolds which
manifolds which
allow greater
allow greater
allow greater
allow greater
residence time for burning HC and CO with oxygen in the pumped in air. For keeping a
flame constantly burning (a
flame constantly burning (and there by assuming complete combustion) a secondary air
nd there by assuming complete combustion) a secondary air
pump injects fresh air into the reactor; this reduces HC and CO. About 10 to 75 percent
of the gas is re
of the gas is re
of the gas is re
of the gas is re-
-
-
-circulated after cooling in the intercooler to reduce the formation of NO
circulated after cooling in the intercooler to reduce the formation of NO
circulated after cooling in the intercooler to reduce the formation of NO
circulated after cooling in the intercooler to reduce the formation of NOx
x
x
x

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
In this packing sy
In this packing sy
In this packing sy
In this packing system are also included the following
stem are also included the following
Enriched and stage carburettor temperature controls;
Crankcase valve to control blow
Crankcase valve to control blow-
-
-
-by gases;
by gases;
by gases;
by gases;
Special evaporation control valves.
In this package emission of NO
In this package emission of NOx
x
x
x ,
,
,
,HC and CO are reduced to a required level but at the
HC and CO are reduced to a required level but at the
co
co
co
cost of 20 per cent less power and 10 per cent more fuel
st of 20 per cent less power and 10 per cent more fuel
st of 20 per cent less power and 10 per cent more fuel
st of 20 per cent less power and 10 per cent more fuel consumption. This
consumption. This
consumption. This
consumption. This converter
converter
converter
converter
can be employed for a run of 1
5
5
5000
000
000
000 km.
km.
km.
km.
Catalytic Converter Package: ( VTU July 2007
Catalytic Converter Package: ( VTU July 2007,July 2006
,July 2006
,July 2006
,July 2006)
)
)
)
The
The
The
The working principle of this package is to control the emission levels of va
working principle of this package is to control the emission levels of va
working principle of this package is to control the emission levels of va
working principle of this package is to control the emission levels of various
rious
rious
rious
pollutants by changing the chemical characteristics of the exhaust gases. The catalytic
converter package as com pared to thermal reactor package requires non
converter package as com pared to thermal reactor package requires non-
-
-
-leaded fuel
leaded fuel
leaded fuel
leaded fuel
as lead reduces the catalytic action.
The major advantage of this converter (a
The major advantage of this converter (as compared to thermal reactor) is that it allows
s compared to thermal reactor) is that it allows
a partial decoupling of emission control from engine operation in that the conversion
efficiencies for HC and CO are very high at normal exhaust temperatures.
Converters for HC and CO and NO
Converters for HC and CO and NOx
x
x
x are arranged
are arranged
are arranged
are arranged as shown in the figure. The NO
as shown in the figure. The NO
as shown in the figure. The NO
as shown in the figure. The NOx
x
x
x
catalyst is the first element in the gas flow path, does not cause release of any heat.
The next is HC/CO catalyst, which releases heat to such a great extent that may cause
overheating and burning of the element. This is t
overheating and burning of the element. This is taken care of by injecting air through
aken care of by injecting air through

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
secondary air pump.
secondary air pump.
secondary air pump.
secondary air pump. A bypass valve ahead of converter is used to increase the
A bypass valve ahead of converter is used to increase the
converter life
converter life
converter life
converter life.
.
.
. For better control of NO
For better control of NO
For better control of NO
For better control of NOx
x
x
x, exhaust gas is circulated via an intercooler back
, exhaust gas is circulated via an intercooler back
to air cleaner. For this system, the power loss
to air cleaner. For this system, the power loss is about 30% and the fuel consumption is
is about 30% and the fuel consumption is
about 10% more than normal.
Oxidizing Systems
Oxidizing Systems
Oxidizing Systems
Oxidizing Systems Catalytic Converter
Catalytic Converter
Catalytic Converter
Catalytic Converter Thermal Reactor
Thermal Reactor
Thermal Reactor
Thermal Reactor
Advantages
Advantages
Advantages
Advantages
R
R
R
Reduction of HC and CO
eduction of HC and CO
eduction of HC and CO
eduction of HC and CO 80
80
80
80-
-
-
-90 %
90 %
90 %
90 % 80
80
80
80-
-
-
-90 %
90 %
90 %
90 %
Reduction of NO
Reduction of NO
Reduction of NO
Reduction of NO No
No
No
No No
No
No
No
Reduction of Aldehydes
Reduction of Aldehydes 50% or more
50% or more
50% or more
50% or more 50% or more
50% or more
50% or more
50% or more
Use sa
Use sa
Use sa
Use same design for all
me design for all
me design for all
me design for all
vehicles
vehicles
vehicles
vehicles
possible
possible
possible
possible possible
possible
possible
possible
Life
Life
Life
Life Up to 80000 km
Up to 80000 km
Up to 80000 km
Up to 80000 km Up to 165000 km
Up to 165000 km
Up to 165000 km
Up to 165000 km
Disadvantages
Disadvantages
Disadvantages
Disadvantages
Cost
Cost
Cost
Cost High
High
High
High High
High
High
High
Volume
Volume
Volume
Volume High
High
High
High Higher
Higher
Higher
Higher
Engine Mounting required
Engine Mounting required No
No
No
No Yes
Yes
Yes
Yes
Weight added
Weight added
Weight added
Weight added Some
Some
Some
Some Significant
Significant
Significant
Significant
Container durability Problem
Container durability Problem Yes
Yes
Yes
Yes Yes
Yes
Yes
Yes
Raises engine com
Raises engine com
Raises engine com
Raises engine compartment
partment
partment
partment
temperature
temperature
temperature
temperature
Depends on location
Depends on location
Depends on location
Depends on location Yes
Yes
Yes
Yes
Requires Non leaded fuel
Requires Non leaded fuel Probably
Probably
Probably
Probably No
No
No
No
Requires air injection
Requires air injection Some do
Some do
Some do
Some do Some do
Some do
Some do
Some do
Lowers fuel economy
Lowers fuel economy
Lowers fuel economy
Lowers fuel economy No
No
No
No Probably yes
Probably yes
Probably yes
Probably yes
Decreases power
Decreases power
Decreases power
Decreases power Depends on back pressure
Depends on back pressure
Depends on back pressure Depends on back pressure
Loss of catalytic material
Loss of catalytic material due
due
due
due
to attrition
to attrition
to attrition
to attrition
Yes
Yes
Yes
Yes No
No
No
No
May emit other toxic material
May emit other toxic material Yes
Yes
Yes
Yes No
No
No
No

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
EFFECT OF ENGINE EMISSION ON HUMAN HEALTH ( VTU July 2007
EFFECT OF ENGINE EMISSION ON HUMAN HEALTH ( VTU July 2007)
)
)
)
The effects of different engine emissions on human health are discussed below:
Sulphur dioxide (SO
Sulphur dioxide (SO
Sulphur dioxide (SO
Sulphur dioxide (SO2
2
2
2)
)
)
)
It is an irritant gas and
It is an irritant gas and affects the mucous membrane when inhaled. In the
affects the mucous membrane when inhaled. In the
presence of water vapour it forms sulphurous and sulphuric acids These acids
cause severe bronchospasma at very low levels of concentration.
Diseases like bronchi
Diseases like bronchitis and astham
tis and astham
tis and astham
tis and asthama are aggravated by a high conc
a are aggravated by a high conc
a are aggravated by a high conc
a are aggravated by a high concentration of
entration of
entration of
entration of
SO
SO
SO
SO2
2
2
2
Carbon
Carbon
Carbon
Carbon-
-
-
-monoxide (CO):
monoxide (CO):
monoxide (CO):
monoxide (CO):
It has a strong affinity (200 times) for combining with the haemoglobin of the
blood to form carboxyhaemoglobin. This reduces the ability of the haemoglobin
to carry oxygen to the blood tissues.
CO affects the central
CO affects the central nervous system.
nervous system.
nervous system.
nervous system.
It is also responsible for heart attacks and a high mortality rate.
Oxides of nitrogen (NO
Oxides of nitrogen (NOx
x
x
x):
):
):
):
These are known to cause occupational diseases. It is estimated that eye and
nasal irritation will be observed after exposure to about 15 p.p.m.
nasal irritation will be observed after exposure to about 15 p.p.m. of nitrogen
of nitrogen
of nitrogen
of nitrogen
oxide, and pulmonary discomfort after brief exposure to 25 p.p.m. of nitrogen
oxide.
oxide.
oxide.
oxide.
It also aggrevates diseases like bronchitis and asthama.
Hydrocarbon vapours:
They are primarily irritating.
They are major contributors to eye and respiratory
They are major contributors to eye and respiratory irritation caused by
irritation caused by
photochemical smog
photochemical smog
photochemical smog
photochemical smog
Compounds of Incomplete combustion
Exhaust discharge from IC engines carry compounds of incomplete combustion
(polycyclic organic compounds and aliphatic hydrocarbons), which act as
carcinogenic agents and are resp
carcinogenic agents and are responsible for lungs cancer.
onsible for lungs cancer.

(ELECTIVE) (ME667)
(ELECTIVE) (ME667)
SIXTH SEMESTER
SIXTH SEMESTER
SIXTH SEMESTER
Lead
Lead
Lead
Lead
Inorganic lead compounds (discharged from vehicles using leaded petrol) cause
a variety of human health disorders.
The effects include gastrointestinal damage, liver and kidney damage,
abnormality in fertility and pregnancy
abnormality in fertility and pregnancy etc.
etc.
etc.
etc.
Smoke
Smoke
Smoke
Smoke
It is visible carbon particles.
It causes irritation in eyes and lungs, and visibility reduction. It also, causes other
respiratory diseases.
Generally speaking,
Generally speaking,
Generally speaking,
Generally speaking, Susceptibility to the effects of exhaust emissions is greatest
Susceptibility to the effects of exhaust emissions is greatest
amongst infants and
amongst infants and
amongst infants and
amongst infants and the elderly. Those with chronic diseases of lungs or heart are
the elderly. Those with chronic diseases of lungs or heart are
thought to be at great risk.
4 stroke I C engine is economical and less pollutant than 2 stroke engine
4 stroke I C engine is economical and less pollutant than 2 stroke engine –
–
–
– Justify.
Justify.
Justify.
Justify.
In two
In two
In two
In two-
-
-
-stroke engine the charge has to be compressed outside for scavenging an
stroke engine the charge has to be compressed outside for scavenging an
stroke engine the charge has to be compressed outside for scavenging an
stroke engine the charge has to be compressed outside for scavenging and
d
d
d
charg
charg
charg
charging
ing
ing
ing (this consumes some engine power). A part of this charge escapes directly
(this consumes some engine power). A part of this charge escapes directly
through
through
through
through exhaust ports (short circuiting). Thus power spent in compressing this fraction
exhaust ports (short circuiting). Thus power spent in compressing this fraction
of the charge is wasted. Particularly in S.I. engines the charge consists of air
of the charge is wasted. Particularly in S.I. engines the charge consists of air-
-
-
-fu
fu
fu
fuel
el
el
el
mixture. This loss of power and charge is absent in 4
mixture. This loss of power and charge is absent in 4-
-
-
-stroke engine. Therefore 4
stroke engine. Therefore 4
stroke engine. Therefore 4
stroke engine. Therefore 4-
-
-
-stroke
stroke
stroke
stroke
engine is always economical than 2
engine is always economical than 2-
-
-
-stroke engine.
stroke engine.
stroke engine.
stroke engine.
Further the loss of charge increases HC in the exhaust in case of two
Further the loss of charge increases HC in the exhaust in case of two-
-
-
-stroke engines,
stroke engines,
stroke engines,
stroke engines,
Hence 4
Hence 4
Hence 4
Hence 4-
-
-
-stroke engine is also
stroke engine is also
stroke engine is also
stroke engine is also less pollutant than 2
less pollutant than 2
less pollutant than 2
less pollutant than 2-
-
-
-stroke engine.
stroke engine.
stroke engine.
stroke engine.

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