Transcript Document 7236874

Traffic Emission Controls
Dr.Wesam Al Madhoun
Emission Controls

Before beginning to understand emission
controls you should know the reason why
emission controls were installed into the
automobile.

1. To reduce the amount of pollutants entering the
atmosphere .

Smog is a term developed from smoke.

Smog is form when airborne pollutants is
formed with oxygen and other atmospheric
gasses to produce a grayish yellow smoke.

The resulting smoke is called photochemical
smog.
Smog

Smog is can be a major problem in larger
cities
(New
York
and
LA)

Smog can be harmful to



A. Humans
B. Plants
C. Animals and even effect paint rubber and
other materials.
Smog

One of largest producer of photochemical
smog is the automotive internal combustion
engine.

The EPA (environmental protection agency)
begin putting restriction on automotive
manufactories in the mid 60.
Motor Vehicle Emissions

Motor
vehicle
emission
are
emission
produce by motor vehicles. They include

A. Hydrocarbons (HC)

Carbon monoxide (CO)

Oxides of nitrogen (NOx)
Exhaust Gasses

Hydrocarbons (HC) are emission of unburned
petroleum products being released into the
atmosphere.

All petroleum products and made of
hydrocarbons
(hydrogen
and
carbon
compounds) this includes:


Gasoline
Diesel
LP-gas.
motor oil.
Exhaust Gasses

Hydrocarbons are produced because of
incomplete
fuel
combustion
or
fuel
evaporation.

Hydrocarbons emission is considered a
hazardous form of air pollution because of.




Eye.
Throat.
Lung irritation.
And possibility cancer.
Exhaust Gasses

In the US a vehicle must not
exceed
220
ppm
of
hydrocarbons emissions.

High hydrocarbon
are the results of a:



emission
cylinder misfire.
Improper ignition timing
Pumping oil into the combustion
chamber
Exhaust Gasses

Carbon monoxide emission are exhaust
emission that is the result of partially burned
fuel.

A high carbon monoxide emission can be
caused by a:



Restricted or dirty air cleaner.
Advance ignition timing.
Clogged fuel injectors.
Exhaust Gasses

Oxides of nitrogen, (NOx) are emission produced
by extreme heat.

Air consist of approximately 79% nitrogen and 21%
oxygen

When combustion chamber temperature reaches
2500 degrees F or 1370 degrees C nitrogen and
oxygen combine to produce oxide of nitrogen
(NOx)

In the US the standard for Carbon Monoxide
is 1.2 % of the total exhaust output.
Muffler
HC 220 ppm
CO 1.2%
Exhaust output
Exhaust Gasses

Oxides of nitrogen is responsible for the dirty
brown color is SMOG.

NOx is a eye and respiratory irritant.

Newer high compression, leaner air fuel
mixture and hotter running engine produces
more NOx than earlier engine.
Exhaust Gasses

The same factors that increases NOx will tend to
improve fuel mileage and lower HC and CO2
production.

This means that to increase fuel economy and
lower HC and CO2 production NOx will increase.

For this reason emission controls have been added
to lower all form of emissions
Exhaust Gasses
NOx
increases
HC increases
Richer
NOx
decreases
14.7 – 1 AFR
Leaner
Hc and Co
decreases
Exhaust Gasses

Before understanding emission controls we need to
first understand where they come from.

Particulates: are solid particle of carbon soot and
fuel additives that blow out the tail pipe.

Engine crank case blow by. Caused by heating of
oil and unburned fuel vapors that blow past the
engine rings.
Exhaust Gasses

Fuel vapors: different chemicals that enter
the atmosphere as fuel evaporates.

Engine exhaust gasses: are harmful
chemical that are produced inside the
combustion chamber and are blow outer the
tail pipe.
HC
Exhaust
manifold
Catalytic
Converter
CO
Solid particulate
Fuel
Tank
Air
Fuel
Vapors
Fuel
Fuel
Fuel
Pump
Exhaust Gasses

Automotive manufactures agree the best
way to lower exhaust emission is to burn all
the fuel entering the combustion chamber.

Modern engine have introduced several
modification to ensure all fuel entering the
combustion chamber is burned.
Some engine modification are:
 Lower compression ratio, by lowering compression
ratio vehicle can burn unleaded fuel.

It is the ratio between the volume of
the cylinder and combustion chamber when
the piston is at the bottom of its stroke, and the
volume of the combustion chamber when the piston
is at the top of its stroke.

The use of unleaded fuel allows for catalytic
converters that help reduce HC and CO emissions.
Lower compression ratio also lower combustion
temperature reducing NOx emission.


Smaller combustion chambers, allows for more
heat to remain inside the combustion chamber that
can aid in the burning of fuel.

Reduce quench areas, the areas between the
piston and the cylinder head is the quench area.

If this areas is too close, fuel will not burn
completely increasing HC and CO emissions.

Modern engine are design to reduce high quench
areas.
Exhaust Gasses
Quench area
Exhaust Gasses

Decrease valve overlap, is used to decrease
exhaust emission.

A larger valve overlap increases power but
dilutes incoming fuel mixture and requires a
richer air fuel mixture at lower engine speed
therefore increasing HC and CO emissions.
Overlap
Intake
Exhaust
Exhaust Gasses

Higher combustion chamber temperature, are
used to reduce HC and CO emissions.

Today vehicles used hot thermostats than earlier model
helping to increase combustion chamber temperature.

Leaner air-fuel mixtures help fuel burn better,
lower HC and CO emissions.

Wider spark plug gaps, are used to burn the
leaner fuel mixture and helps prevent spark plug
fouling.
Wider spark plug gap
Thermostats are
now 190 degrees
Vehicle Emission Control

There are several different types of
emission control system used on modern
vehicles.

Positive crankcase ventilation system
(PCV) is used to re-circulate engine
crankcase
fumes
back
into
the
combustion chamber.

A PCV valve uses manifold vacuum to draw blowby gasses from the engine into the intake
manifold for re-burning by the engine.

In earlier years automotive manufactories uses
road draft tubes to remove crankcase blow by
gasses.
Vehicle Emission Control

The uses of road drift tube allowed for blow
by gasses containing HC, CO, particulates,
sulfur and small amounts of water to be
vented in the atmosphere.

At idle when there is high engine vacuum
the PCV valve is opened to remove blow-by
gasses from inside the engine.
Vehicle Emission Control
When engine Vacuum is High PCV valve
plunger is nearly closed
When engine vacuum is low plunger Opens.
Allowing exhaust gasses into Engine.
PCV
Plunger
Typical PCV valve
Evaporative Emissions Control Systems
EVAP

The EVAP system prevents Hydrocarbons in the
form of fuel vapors from entering the atmosphere
even when the vehicle is not running.

An EVAP system is considered a closed system.

Fuel vapor are stored in a charcoal canister when
the engine is off.

When the engine is started vacuum pulls fuel
vapors into the engine for burning.

EVAP system different from per emission vehicle
because no fuel or vapor is vented into the
atmosphere.
Unvented Fuel Cap
Intake
Manifold
Vacuum
Rollover Valve
Charcoal Canister
Fuel Tank

A rollover valve is uses to prevent fuel spillage in
case of a rollover.

A liquid-vapor separator is sometime used to
prevent liquid fuel from entering the charcoal
canister.

A charcoal canister is used to store fuel vapor when
the engine is not operating.
Exhaust Gas Recirculation System
(EGR)

An EGR system has two important jobs
1. The recirculation system is used to burn unburns gasses (HC and CO) By recirculation of unburn gasses lower emissions can be achieved.
2.Lowering combustion chamber temperature. By
lowering combustion chamber temperature NOx
emission can be lowered.
0
Vacuum Gauge
Vacuum
off
throttle
Exhaust Gasses
Exhaust Gasses to Engine

EGR Valve
Charcoal Canister
Catalytic Converters

In the mid 70s automotive manufacture
begin installing catalytic converters to assist
in meeting tougher emission standards.

A Catalytic is a material that can speed-up
chemical action without changing itself.
Catalytic Converters

Automotive catalytic converter are made of
platinum, palladium and rhodium or a
combination of these materials.

Platinum and palladium are used to change
HC and CO into CO2 and Water.

Rhodium acts to reduce NOx emissions
Catalytic Converters

Due to enhance emissions standard, later
model catalytic converters now use cerium
to attract and release oxygen inside the
converter to aid in the process of changing
HC and CO to CO2 and H2o

The catalyst agent inside a catalytic converter is
either ceramic beds or a honeycomb-shaped blocks.

All catalytic converters are encased in a stainless
steel housing.

NOTE: stainless steel is used on newer vehicle with
catalytic converters because the production of water
will rust traditional exhaust system in only a few
years
Catalytic Converter
Engine
HC and CO
Exhaust Flow from engine
through converter
CO2
H2o
Catalytic Converters

Stainless steel catalytic converter housing
are design to resist heat.

Before the catalytic converter can operate,
an operating temperature of around 300
degrees F must be reached.

This is a
converter.
honey-comb
block
type
catalytic

Exhaust gasses flow through the honey-comb
block


There are a few different types catalytic
converters.

Monolithic Converter

Two way converter

Three way converter

Dual bed converter
Monolithic converter uses a ceramic honey-comb
catalytic

Two way catalytic converters only convert
HC and CO

With a two way converter NOx is not
converted

Two way converter are coated with platinum
only

Two way converter are sometime referred to
as oxidation converters
Catalytic Converters

Three way catalytic converters can convert
all three exhaust gasses



HC
CO
NOx
Catalytic Converters

A three way catalytic converter is usually
plated with rhodium and platinum

Three way converter
reduction converters.
are
also
called
Catalytic Converters

Dual bed catalytic converter is an oxidation
and reduction converter built into one unit.
CO2 and H20
CO,
HC
and
NOx
Mixing Chamber
Catalytic Converters

Dual bed catalytic converters must be at an
operating temperature of 130 degrees F

When the engine is cold additional air is
forced into the exhaust manifold to aid in the
burning and reduction of HC and CO
Catalytic Converters

On a warn engine, air is forced into the converter
to aid in burning exhaust gasses.

As exhaust gasses flows into the front part of the
converter, HC,CO and NOx is reduced.

As exhaust flow into the mixing chamber,
additional air is added to continue the burning
process.

Exhaust gasses passed into the rear part of the
converter to reduce HC,CO2 and NOx ever more.