traffic emission controls

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 LP-gas. Diesel 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 emission are the results of a: 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

Exhaust output

HC 220 ppm

CO 1.2%

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

14.7 – 1 AFRRicher Leaner

HC increases

NOx decreases

NOx increases

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.

Fuel

Air

Exhaust manifold

Catalytic Converter

Fuel Tank

Fuel Pump

HC

CO

Solid particulate

FuelFuel

Vapors

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 blow-by 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.


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.


When engine Vacuum is High PCV valve plunger is nearly closed

When engine vacuum is low plunger Opens. Allowing exhaust gasses into Engine.

PCVPlunger

Typical PCV valve

Evaporative Emissions Control SystemsEVAP

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

Rollover Valve

Charcoal CanisterFuel Tank

Intake Manifold Vacuum

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 un-burns gasses (HC and CO) By recirculation of un-burn gasses lower emissions can be achieved.

2.Lowering combustion chamber temperature. By lowering combustion chamber temperature NOx emission can be lowered.

Exhaust Gasses

Exhaust Gasses to Engine

Vacuum off throttle

0 Vacuum Gauge

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.


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


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

HC and COCO2 H2o

Catalytic Converter

Engine

Exhaust Flow from engine through converter


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 honey-comb block type catalytic converter.

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


Three way catalytic converters can convert all three exhaust gasses

HC CO NOx


A three way catalytic converter is usually plated with rhodium and platinum

Three way converter are also called reduction converters.


Dual bed catalytic converter is an oxidation and reduction converter built into one unit.

Mixing Chamber

CO, HC and NOx

CO2 and H20


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


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.

traffic emission controls

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