This PPT will gives the information about Air Pollution due to Automobiles, types of pollutants produced and their control measures

1. INTRODUCTION
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Automotive emissions in aggravating the air pollution
and various causes of the genesis and exodus of
these pollutants have been identified and methods to
control them have been outlined.
The three main types of automotive vehicles being
used in our country are:
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Passenger cars powered by four stroke gasoline engines
Motor cycles scooters and autorickshaws powered mostly
by small two stroke engines,
Large buses and trucks powered mostly by four stroke
diesel engines,

2. Contd…
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Emissions from gasoline powered vehicles are
generally classified as:
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Exhaust emissions
Crank case emissions
Evaporative emissions
The amount of pollutants that an automobile emits
depends on a number of factors including the design
and operation.
Diesel powered engines create relatively minor
pollution problems compared to gasoline powered
ones.
The major problems of diesel engines are smoke
and odor.

3. EXHAUST EMISSIONS

The important exhaust emissions from a gasoline
engine are
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carbon monoxide,
unburnt hydrocarbons,
nitrogen oxide and
particulates.
Automobile manufactures have used two basic
methods:
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The first is to inject manifold near the exhaust valves,
where exhaust gas temperature is highest, thus inducing
further oxidation of unoxidised or partially oxidised
substances.
The second basic method is to design cylinders and
adjust fuel-air ratio, spark timing and other varaibles to
reduce the amounts of hydrocarbons and CO

4. Contd….
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Devices and methods to control
emissions fall into three classes
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hydrocarbon
Devices that modify engine operating conditions such as
intake manifold vacum breakers, carburation mixture
improvers, throttle retraders,
Devices that ‘Treat” exhaust gases such as after burners,
catalytic converters, absorbers and filters
Use of modifies or alternate fuels.

5. CRANK CASE EMISSIONS

Crank case emissions consist of engine blow by
which leaks past the piston mainly during the
compression stroke and of oil vapours generated
into the crank case.

6. Contd…
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The gases mainly contain hydrocarbons and account
nearly for 25% of the total hydrocarbon emissions
from a passenger car.
Emissions of hydrocarbons from the crank case of
automobiles can be largely eliminated by the positive
crank case ventilation(PCV) systems.
These systems recycle crank case ventilation air and
blowby gases to the engine intake instead of venting
them to the atmosphere.

7. EVAPORATIVE EMISSIONS
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It has been estimated that an average Indian
passenger car would emit about 20kg of
hydrocarbons through evaporation annually.
It might also be dealt with by changing the properties
of gasoline such as reducing the volatility of fuel and
replacing the C4 and C5 olefinic hydrocarbon in the
fuel with the less reactive C4 and C5 paraffinic
hydrocarbons.
Mechanical methods can also be used to control
evaporative emissions.
The exhaust gas pollutants comprise of
hydrocarbons, carbon monoxide, nitrogen oxides
and lead compounds.

8. FORMATION OF PHOTOCHEMICAL SMOG
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The deleterious effects of automotive pollutants
include toxic effects of CO and lead compounds and
the formation of photochemical smog.
The chief culprits in the smog dilemma are the
volumetrically lower concentrations of unburnt or
partially burnt hydrocarbons and nitrogen oxides.
The necessary conditions for smog formation are:

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Sufficient quantity and concentration of unburnt
hydrocarbons and nitrogen oxides in the atmosphere
Stagnant
atmospheric
conditions
produced
by
meteorological thermal inversions
Strong sunlight.

11. AIR-FUEL RATIO
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A decrease in the AF ratio increases the HC content
in the exhausts of passenger cars at idle, but does
not have any effect at part throttle.
Methane and acetyleene are the two hydrocarbons
most greatly affected by the AF ratio.
Spark Timing:
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The HC emission generally decreases as the spark is
retrated at constant power.
Combined Effects of AF Ratio and Spark Timing:

The reductions in HC emission due to leaner AF ratios
and due to retarted spark timing are additive.

12. COMBUSTION CHAMBER SURFACEVOLUME RATIO
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The effects of combustion chamber S/V ratio on the
exhaust emissions have been investigated by
Scheffer.
Engines with S/V covering a wide range were
installed in cars and tested according to the
California schedule.

13. Contd…
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It has been found that when S/V is decreased by
decreasing CR, a greater reduction in HC emission
is obtained that when S/V is decreased by changing
other variables.

14. COMBUSTION CHAMBER DEPOSITS
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HC exhaust emissions are significantly enhanced
with accumulation of chamber deposits.
During combustion, these pores and their
interconnecting passsages are filled with unburnt HC
and escape burning.
These are discharged back to the atmosphere during
exhaust in the same state, increasing emission
levels considerably.
Uniform distribution of deposits is likely to provide
more void space for the adsorption on unburnt HC
during combustion thereby raising exhaust levels

15. CONTROL OF EXHAUST EMISSIONS
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Two main approaches to minimize exhaust
emissions are:
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Modifications in the engine design and operating
variables.
Treatment of exhaust gases after emission from the
engine.
The following modifications may help in cleaner
exhaust
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Use of leaner idle mixture
Use of leaner possible mixture and maximum spark retard
compatible with good power output and drivability.
Use of minimum valve-over-lap necessary
Pre-treatment of the mixture to improve vaporization and
mixing of fuel with air.

16. Contd…
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Among the methods employed for the purpose are:
Use of narrow venturies to produce higher air speeds and
better fuel atomisation
 Provision of exhaust heated hot spots to vaporise the
heavier liquid droplets in the airstream,
 Use of exhaust het to pre heat the mixture at part loads
 Use of automatic transmission
 Special devices for reducing or cutting off fuel supply
during deceleration.


17. Contd…

18. 
Exhaust Treatment Devices:
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Promotion of after burning of the pollutants by exhaust
heat conservation, introduction of additional air and by
poviding sufficient volume to ensure adequate reaction
time.
Use of catalytic convertors
Catalytic converters depend on the action of a
catalyst containing certain exotic chemicals to
convert HC and CO emissions to their oxidised
products.
How ever they have certain limitations:
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Poisoning of catalyst by lead compounds in fuel
Deterioration with time
Pressure loss and noise problems

19. 
Other Methods:
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Petrol Injection:
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The petrol injection system provides the flexibility needed to
meet the engine requirements and eliminates the problem of
mixture distribution altogether and hence has lower levels of
exhaust emissions and better specific fuel consumption.
Stratified Charge Engine:

It operates with very lean air petrol mixtures depending on a
localised rich mixture region near the spark plug to initiate
combustion

20. NITROGEN OXIDES IN EXHAUST GAS
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The concentration of NOx in exhaust gas is found to
depend mainly on the peak temperature and
pressure and the supplied air fuel mixture
composition.
The NOx concentration rises rapidly as the mixture is
made leaner around the stoichiometric ratio of 14.6.

21. Contd…
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The following are the methods have been tried to
reduce the concentration of oxides of nitrogen:
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Exhaust gas recycling
Water injection into inlet manifold
Exhaust manifold reactor with recycling
Catalytic reduction
Lean operation

22. CONTROL OF EVAPORATIVE EMISSIONS
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There are two sources of evaporative emissions viz.,
the fuel tank and the carburettor.
The principal factors governing tank emissions are:
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Fuel volatility
Ambient temperature
Tank emissions
Carburettor emissions may be divided into two
categories:
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Running losses occurring during engine operation and
Hot soak losses occurring when the vehicle is parked.

23. CONTROL OF CRANK-CASE EMISSIONS
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These consist of engine blowby gases, ventilation air
and crank-case lubricant fumes.
For air pollution blowby is most important and the
principal constituents in blowby gases are
hydrocarbons.
Designers are shifting crank-case exhaust vents
from simple open ending to a feed back.
New engines equipped with this positive crank-case
ventilation (PCV) system return crank-case vapours
through a vacuum valve, back to the downstream
side of the carburettor.

24. Contd…

25. ALTERNATIVES
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Electric car
Natural gas
Wankel Engine
Gas Turbine
Ammonia-fueled SI Engine
Unleaded-gasoline Powered SI Engine

26. AIR POLLUTION DUE TO AUTOMOBILES IN
CALCUTTA
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NEERI carried out a short-term survey in Calcutta to
collect information on the level of CO pollution due to
automobile exhausts.
High traffic density streets in Calcutta were studied
by measuring CO levels during different phases of
traffic;
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Heavy traffic
Traffic jams with slow movement,
Normal and light traffic
It was observed that the level of CO due to auto
exhausts at street level varied from a high as 35ppm
to less than 10 ppm at all selected streets depending
upon the traffic conditions.

27. Contd…
City
London
46
Los Angeles
43
Washington
41
New York
27
Calcutta
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58
Chicago
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Maximum 1 hr values – ppm
35
The Calcutta data shows that although the number of
vehicles in Indian cities is smaller compared to western
cities, yet the intensity of pollution caused by them is
apparently the same, if not more.
This can be attributed to old vehicles with poor engine
performance